6/6/25 MRI

Question 1

What does MRI stand for?

Answer 1

Magnetic resonance imaging

Question 2

Magnetic resonance relates to interaction with ______.

Answer 2

Nuclei

Question 3

What % of the human body is made up of oxygen, nitrogen, carbon, and hydrogen?

Answer 3

96%

Question 4

What is the atomic number for H+?

Answer 4

1

Question 5

How does MRI use our body’s hydrogen ions to generate images?

Answer 5

Hydrogen ions in our body act like little magnets, possessing both a charge and a spin. The spinning protons act like small, weak magnets. We can align these magnets so they release energy into a signal that is received by the scanner and converted into images.

Question 6

What magnetic field strengths do we use for clinical imaging?

Answer 6

0.5-3 Tesla

Question 7

If someone has a medical implant, would we want to use 1.5T or 3T?

Answer 7

1.5 T. Even though 3T generally provides better imaging, it could make the implant look worse on imaging, skewing the image.

Question 8

What are the 2 types of MRI scanners?

Answer 8

Open Magnet Scanners
Closed Magnet Scanners

Question 9

What are the pros and cons of open magnet scanners?

Answer 9

Pro: Less claustrophobic
Con: Less field strength

Question 10

What are the pros and cons of closed magnet scanners?

Answer 10

Pro: More field strength
Con: More claustrophobic

Question 11

What are the 4 main components of an MRI scanner?

Answer 11

The Bore
Primary Magnet
Gradient Magnet
RF coils

Question 12

What is the bore of the MRI scanner?

Answer 12

The big tube that houses all the other MRI components

Question 13

What is the primary magnet of the MRI scanner?

Answer 13

A magnet made up of huge loops of wire that conduct electricity resulting in a powerful magnetic field (housed in cold liquid helium)

Question 14

What is the gradient magnet/coil of the MRI scanner?

Answer 14

The magnet that allows for the production of the gradients in the X-Y-Z planes to help localize image slices

Question 15

What are the RF coils of the MRI scanner?

Answer 15

These coils are what are sending the RF pulse to realign the hydrogen protons

Question 16

True or False: RF coils can transmit and receive signals

Answer 16

True

Question 17

The closer an RF coil is to the area of interest, the _____ the image quality.

Answer 17

Better

Question 18

Are MRI magnets always on?

Answer 18

Yes, difficult to turn off, because would have to remove all the liquid helium)

Question 19

What MRI zone contains the magnet?

Answer 19

Zone 4 (no metallic objects here!!!)

Question 20

What MRI zone contains the control room and the computer room?

Answer 20

Zone 3

Question 21

What MRI zone has patient reception and waiting room areas?

Answer 21

Zone 2

Question 22

What is the projectile/missile effect?

Answer 22

External ferromagnetic objects can injure patients as they are pulled towards the magnet (scissors, oxygen tanks)

Question 23

What can MRI cause displacement of?

Answer 23

Intra-corporeal metallic foreign objects (metal in eye, cochlear implants, aneurysm clips, vascular stents)

Question 24

MRI can cause malfunctioning of what medical devices?

Answer 24

Cochlear implants
Pacemakers
Neurostimulators

Question 25

What does SAR stand for?

Answer 25

Specific absorption rate

Question 26

What is gradient switching?

Answer 26

Rapid switching of gradient pulses which can sometimes lead to stimulation of peripheral nerves/muscles (rare)

Question 27

SAR: How can RF pulses be harmful to a patient?

Answer 27

They can deposit energy into tissues which can lead to heating/burns

Question 28

If a patient comes into the ED unresponsive and needs an MRI, what is done first?

Answer 28

A panscan which is X-ray ot CT of major body parts to rule out the presence of medical implants/medical devices

Question 29

MRI is generally considered safe in pregnancy. Can MRI contrast still be used in pregnancy?

Answer 29

No

Question 30

What component of the MRI machine is responsible for all the loud noises?

Answer 30

The gradient coils

Question 31

What are some clinical considerations when ordering an MRI?

Answer 31

Can patient follow directions? Can patient lay flat for long periods? Is patient claustrophobic? Does patient need sedation? Can patient hold their breath? Does the patient have an arrythmia> Is the patient pregnany?

Question 32

What type of contrast is used for MRIs?

Answer 32

Gadolinium based

Question 33

Why is there concern about using gadolinium as an MRI contrast agent?

Answer 33

It can deposit in the brain. Free gadolinium can be toxic, so there is question about its long term effects on the human body. Does not seem to have any bad symptoms or diseases associated with it, but it is avoided when possible.

Question 34

What are some advantages of MRI?

Answer 34

No radiation Good contrast Good tissue discrimination Contrast less nephrotoxic Can produce 3D images in any plane, any thickness

Question 35

What are some disadvantages of MRI?

Answer 35

Time-consuming Expensive Patient dependent (function) Claustrophobic Limitations due to metal (pacemaker)