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Flashcards in MRI - PPT Deck (40):
1

Who discovered the properties of MRI?

1940s
Bloch & Purcell

2

Who produced 1st MRI image of a human being?

1977
Damadian

3

Who awarded Nobel Prize in Physiology for discoveries in MRI?

2003
Lauterbur & Mansfield

4

Who produced 1st MRI image of an object?

1973
Lauterbur

5

When was 1st MRI equipment became available for
installation?

1980s

6

MRI depends of

The properties of the nucleus of an atom

7

Hydrogen is used since

It is the most abundant element in the body

8

Hydrogen with a single proton in its nucleus is

The strongest nuclear magnet, therefore creating the strongest MRI signal

9

RF (radiofrequency) coils are

"antenna" of the MRI system that broadcasts the RF signal to the patient and/or receives the return signal
(Received signals & send feedback)

10

Gradient coils are used to

- Produce deliberatevariations in the main magnetic field (Bo).
- There are usually three sets of gradient coils, one for each direction (x, y, z axes)

11

Resistive magnets

- Simple, large electromagnets
- Limited field strength (no more than 0.6 T)

12

Superconductive (cryogenic) magnets

- Electromagnets that use liquid helium for cooling
- Permits higher magnet strengths than resistive magnets

13

Permanent magnets

- Does not require electricity or cooling
- Heavy, massive
- Smaller fringe field

14

Clinical MRI uses

Superconductive (cryogenic) magnets

15

Magnetic field strength is measured in

tesla (T) or gauss (G)
1 T = 10,000 G

16

Earth’s natural magnetic field is

0.5 G

17

Low-field magnets range is

0.2 T – 1.0T

18

High-field magnets range is

1.5T and higher

19

FDA has approved up to ....................... magnets for clinical imaging of babies and up to 8T for clinical imaging of adults and children

4T

20

Outside the U.S., up to ................ can be used

15T
(China 27T)

21

Patient Table is

Hydraulically or mechanically driven
Magnetically safe and contain no metal parts

22

Patient Table Must allow for

attachment of coils and immobilization devices

23

Patient Table Weight limits range from

300 – 660 lbs

24

T1‐weighted image is Used to evaluate

- Anatomy (structure)
• Characterized by bright fat & dark water

25

T2‐weighted image is Used to evaluate

- Pathology
• Characterized by bright water & dark fat

26

2 Types of Contrast Media

1. Gadolinium compounds
2. Iron oxide mixtures

27

Gadolinium compounds also called

Paramagnetic substance
T1 agent

28

Gadolinium compounds is

- Most commonly used
- Lower toxicity and fewer side effects than iodinated IV contrast
- Used in the evaluation of the CNS and for tumor detection

29

Iron oxide mixtures also called

Superparamagnetic substance
T2 agent

30

Iron oxide mixtures is used to

Detect and diagnose liver lesions

31

MRI Safety: 4 Basic Areas of Concern

• Thermal injuries
• Acoustic noise
• Projectiles
• Nephrogenic Systemic Fibrosis

32

Thermal Injuries

Burns can result when:
• Cables from coils are in contact with the
patient’s skin
• Metals, wires, medication skin patches with
foil, and ferromagnetic inks from tattoos are
present in the scanner

33

Acoustic Noise

- MRI can produce noise up to 130 dB
- Ear plugs can reduce the noise by 10-30 dB

34

Projectiles

The missile effect
the force with which projectiles are pulled towards a magnetic field is proportional to:
• the strength of the magnet
• the distance from the magnet
• the mass of the object
• the material that the object is made of

35

Ferromagnetic metal object can reach a
terminal velocity of ...................when pulled into a
............................ magnet

40 mph
1.5T

36

MRI offers

superior imaging of soft-tissue structures

37

MRI does NOT use

ionizing radiation

38

MRI Contrast material is better tolerated compared to

Radiography and CT

39

Proper patient screening is

utmost importance

40

the magnet is ALWAYS

ON