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Physics > DUBOSE VIDEO REVIEW > Flashcards

DUBOSE VIDEO REVIEW Flashcards

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1
Q

What zone is where the scanner is at?

A

Zone IV

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2
Q

What zone is where the computer console is at?

A

Zone III

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3
Q

Who is allowed in Zone III?

A

Level I and Level II

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4
Q

The tunnel of the MRI machine is the?

A

Bore

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5
Q

The gravitational pull of the earth?

A

.5 G; we need to know the gravitational pull because we need to know exactly how strong 1T is

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6
Q

1 Tesla is how many gauss?

A

10,000 G

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7
Q

1.5 Tesla is how many gauss?

A

15,000 G

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8
Q

3 Tesla is how many gauss?

A

30,000 G

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9
Q

The atom most commonly used for clinical MR?

A

Hydrogen

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10
Q

What is the atomic number?

A

Number of protons

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11
Q

What happens if you change the number of protons?

A

You change the element

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12
Q

What is the mass number?

A

Number of protons and neutrons

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13
Q

What happens if the mass number is uneven?

A

Isotopes

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14
Q

What is an ion?

A

Number of protons and electrons do not match

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15
Q

More electrons than protons and its negative, we call it?

A

Anion

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16
Q

More protons than electrons and its positive we call it?

A

Cation

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17
Q

The main magnetic field is aka?

A

B0 or static field

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18
Q

The secondary field produced by RF is known as?

A

B1

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19
Q

What is NMV?

A

Protons we are playing with after cancelling out and this is where the signal is coming from

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20
Q

What letters do we represent NMV?

A

M

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21
Q

What is M subscript Z?

A

Longitudinal plane

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22
Q

What is M subscript X Y?

A

Transverse plane

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23
Q

What plane is the NMV in?

A

Transverse plane

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24
Q

What is M negative Z?

A

180

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25
Q

MXY is everything in between and they’re spinning and transverse is anything between what numbers?

A

1- 179

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26
Q

3 magnet types?

A
  • Permanent
  • Resistive
  • Superconducting
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27
Q

What 2 magnet types are electromagnets?

A

Resistive and superconducting

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28
Q

What is electromagnet?

A

Magnet that is produced by flowing electricity

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29
Q

If you turn off the electricity, what happens to magnetic field?

A

It goes away unless it is superconductive

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30
Q

Superconducting magnets are at what kelvin?

A

4 Kelvin

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31
Q

How do we get down to 4 kelvin?

A

Cryogen (liquid helium) close to absolute zero

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32
Q

4 Kelvin is what celsius and Fahrenheit?

A
  • 269 Celsius
  • 452 Farenheit
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33
Q

What happens when liquid helium escapes into the room?

A

Quench

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34
Q

In the event of a quench what do we need to do with patient?

A

Get them out of the room

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35
Q

What are the physical dangers of quench?

A
  • Pressure build up
  • Rupture ear drum
  • No oxygen; difficulty to breathe
  • Loss of consciousness
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36
Q

Slightly repelled?

A

Diamagnetism

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37
Q

Gadolinium is what “ISM?”

A

Paramagnetism

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38
Q

Slighlty attracts?

A

Paramagnetism

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39
Q

Strongly attracts?

A

Ferromagnetism

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40
Q

What’s the problem with resistive magnets?

A

It gets weak and very hot

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41
Q

Which magnet is most expensive to buy?

A

Superconducting (ramp it up and unplug it from the wall, the only electricity you are using from that point forward is to run all computers, gradients, etc)

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42
Q

What happens if you unplug resistive magnets from the wall?

A

No more magnet

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43
Q

What happens if you unplug permanent magnets from the wall?

A

Will still have a magnet

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44
Q

Which magnet is the heaviest?

A

Permanent

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45
Q

Which magnet has the largest fringe field?

A

Superconducting

46
Q

What are the dangers of having a strong fringe field?

A
  • Missile or projectiles
  • Tourque
47
Q

How long do you have to wait for post op?

A

6-8 weeks so it can develop scar tissue

48
Q

How do we protect the homogeneity of our main magnetic field?

A

Shielding

49
Q

If its not called Faraday’s cage, it could be?

A

RF shielding

50
Q

What does RF shielding or Faraday’s cage do?

A

It blocks RF from getting into the room; only shielding that stops from getting in

51
Q

2 diff types of shielding for the flux lines?

A

Passive and active

52
Q

If something is active, what can you automatically assume?

A

It is an electromagnet or some type of power

53
Q

Sheets of iron or steel is what shielding?

A

Passive

54
Q

How fast the hydrogen protons are spinning within the scanner is known as?

A

Precession

55
Q

Why does a homogenous field matter?

A

To make sure they are spinning the exact same frequency

56
Q

How do we figure out what frequency they’re spinning at?

A

Larmor equation

57
Q

What is larmor equation?

A

gyromagnetic ratio of hydrogen at 1 T (42.6)
42.6 multiply by the strength of main magnetic field and it will tell you precessional frequency

58
Q

Hydrogen protons within that field will be precessing at the exact same rate and why do we need to know that or why does that have to happen?

A

For resonance

59
Q

What is resonance?

A

RF pulse

60
Q

If the precessional frequency matches, then the RF coil is able to deposit energy into the hydrogen protons. If we deposit energy into the hydrogen protons, the NMV becomes higher energy protons and….

A

flip angle 90 degrees to transverse plane

61
Q

More energy means what to patient?

A

Increase SAR

62
Q

What is TR?

A

Repetition time; amount of time from one excitation pulse to the next

63
Q

What is T1 relaxation?

A

Time it takes for 63% of NMV to realign with main magnet
NMV relaxes back to B0

64
Q

Why do we have dark water on T1 weighted image?

A

It becomes saturated

65
Q

What is TE?

A

Time from excitation RF pulse to sampling of echo signal

66
Q

Which is shorter/faster TR or TE?

A

TE (page 26)

67
Q

What is T2 relaxation?

A

Time it takes for 63% of transverse magnetization

68
Q

For a T2 weighted exam, what TE do you program into the machine?

A

Long TR, long TE

69
Q

Relaxation time for water?

A

Approx 2500 MS

70
Q

Relaxation time for fat?

A

200 MS

71
Q

**** If you want a T1 weighted image, what kind of TE do you have? **

A

Short

72
Q

If you want a T2 weighted image, what kind of TE do you have?

A

Long

73
Q

TE is 100 MS, is that short or long?

A

Long

74
Q

What is the worst thing we can do to our magnetic field?

A

Put a patient in it and it will no longer be homogenous

75
Q

The pre scan is what?

A

Active shimming; evening out the field and ready for the actual scan to start

76
Q

How is the homogenous fields measured?

A
  • Parts per million (PPM)
  • Clinical scanning is 4-10 PPM
  • Spectroscopy is 1 PPM
77
Q

What is the term for flashes of light?

A

Magnetophosphenes

78
Q

Nerves are conductors
True or false?

A

True; walking across a magnetic field you are in motion and you will induce a current in your own nerves

79
Q

Another name for translation?

A
  • Projectiles
  • Missiles
80
Q

Another name for rotation?

A

Torque

81
Q

Burns come from what?

A

B1 (RF) that burns the patient

82
Q

What kind of EKG issues can you have?

A

Elevated T waves and its an issue because of cardiac gating; if you are doing some type of cardiac gating, the machine is looking for the R wave because the TR at that point becomes R wave to R wave and so with an elevated T, sometimes it mistakes the elevated T for an R and it will mess up the cardiac gating

83
Q

The idea that moving a conductor through a magnetic field will induce a current is known as which law?

A

Farday

84
Q

A foreign body that is implanted in the patient and it might be safe but when you cross the flux line and lay them down there is resistance as it is crossing the flux lines is known as which law and what can you do with the patient?

A

Lenz’s law; turn them sideways and that should cut across the flux lines

85
Q

If you have an actively shielded magnet VS a non active shielded magnet, which one is more dangerous for missile effects and why?

A

Active shielding; stronger field when you cross the 5G line

86
Q

Peripheral nerve stimulation is a direct result of what?

A

Gradient fields because they are rapidly reversing time varying magnetic fields

87
Q

How hot can you make the patient, you can elevate their body temperature to?

A

1 degree celsius

88
Q

TR is what T?

A

T1

89
Q

TE is what T?

A

T2

90
Q

Resonance occurs after RF pulse
True or false?

A

True

91
Q

What is the term for half of an echo or the graphic illustration of your T2 decay?

A

FID (Free Induction Decay) ; it appears following the original excitation pulse

92
Q

How do you obtain proton density?

A

Short TE, long TR (combination of T1 and T2)

93
Q

The difference between 2 similar, but not identical tissues is known as?

A

Contrast resolution

94
Q

Examples of Intrinsic? (we can’t control)

A
  • T1 recovery
  • T2 decay
  • Proton density
  • Flow
  • Diffusion
  • Perfusion
95
Q

Examples of Extrinsic? (we can control)

A
  • TR
  • TE
  • Flip angle
  • NSA
  • Receive bandwidth
  • Echo train length/turbofactor
  • TI
96
Q

Another name for bright areas of final image?

A
  • Hyperintense
  • High signal
  • White
97
Q

Another name for dark areas of final image?

A
  • Hypointense
98
Q

Another name for same shade of gray?

A

Isointense

99
Q

Between fat and water, what has the lowest inherent energy?

A

Fat (short T1 relaxation time, short T2 decay)

100
Q

A pulse sequence that begins with a 90 degree RF pulse followed by a180 degree RF pulse is known as?

A

Spin echo pulse sequence

101
Q

To obtain a T1 weighted image, a _____ (short/long) TR is used to ______ (maximize/minimize) T1 effects

A

Short; maximize

102
Q

To obtain a T1 weighted image, a _____ (short/long) TE is used to ______ (maximize/minimize) T2 effects

A

Short; minimize

103
Q

During T2 relaxation, why would fat (or water) molecules lose coherence once the RF pulse is removed?

A

Because of spin spin interaction

104
Q

Parallel and antiparallel creates?

A

NMV

105
Q

Which one has the most? Parallel or antiparallel?

A

Parallel; otherwise we wouldn’t have NMV because we can only play with parallel protons

106
Q

What was MRI originally called and why was it changed?

A

Nuclear magnetic resonance; changed it because were intimated of the name after WW2

107
Q

1 kilo hertz is how many hertz?

A

1,000

108
Q

1 mega hertz is how many hertz?

A

1 million

109
Q

Know SAR limits

A

Ch 10

110
Q

IEC regulation limits for noise of the machine?

A

99 DCB

111
Q

Is there an FDA limit for the time varying gradient fields?

A

No; it is what the patient can tolerate

112
Q

Is pregnancy an issue?

A
  • Possible for amniotic fluid can get hot, some places can say no scanning for 1st trimester
  • For techs, no issues just don’t be in the room during scan

Physics (6 decks)

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