DUBOSE VIDEO REVIEW Flashcards
(112 cards)
1
Q
What zone is where the scanner is at?
A
Zone IV
2
Q
What zone is where the computer console is at?
A
Zone III
3
Q
Who is allowed in Zone III?
A
Level I and Level II
4
Q
The tunnel of the MRI machine is the?
A
Bore
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
6
Q
1 Tesla is how many gauss?
A
10,000 G
7
Q
1.5 Tesla is how many gauss?
A
15,000 G
8
Q
3 Tesla is how many gauss?
A
30,000 G
9
Q
The atom most commonly used for clinical MR?
A
Hydrogen
10
Q
What is the atomic number?
A
Number of protons
11
Q
What happens if you change the number of protons?
A
You change the element
12
Q
What is the mass number?
A
Number of protons and neutrons
13
Q
What happens if the mass number is uneven?
A
Isotopes
14
Q
What is an ion?
A
Number of protons and electrons do not match
15
Q
More electrons than protons and its negative, we call it?
A
Anion
16
Q
More protons than electrons and its positive we call it?
A
Cation
17
Q
The main magnetic field is aka?
A
B0 or static field
18
Q
The secondary field produced by RF is known as?
A
B1
19
Q
What is NMV?
A
Protons we are playing with after cancelling out and this is where the signal is coming from
20
Q
What letters do we represent NMV?
A
M
21
Q
What is M subscript Z?
A
Longitudinal plane
22
Q
What is M subscript X Y?
A
Transverse plane
23
Q
What plane is the NMV in?
A
Transverse plane
24
Q
What is M negative Z?
A
180
25
MXY is everything in between and they're spinning and transverse is anything between what numbers?
1- 179
26
3 magnet types?
- Permanent
- Resistive
- Superconducting
27
What 2 magnet types are electromagnets?
Resistive and superconducting
28
What is electromagnet?
Magnet that is produced by flowing electricity
29
If you turn off the electricity, what happens to magnetic field?
It goes away unless it is superconductive
30
Superconducting magnets are at what kelvin?
4 Kelvin
31
How do we get down to 4 kelvin?
Cryogen (liquid helium) close to absolute zero
32
4 Kelvin is what celsius and Fahrenheit?
- 269 Celsius
- 452 Farenheit
33
What happens when liquid helium escapes into the room?
Quench
34
In the event of a quench what do we need to do with patient?
Get them out of the room
35
What are the physical dangers of quench?
- Pressure build up
- Rupture ear drum
- No oxygen; difficulty to breathe
- Loss of consciousness
36
Slightly repelled?
Diamagnetism
37
Gadolinium is what "ISM?"
Paramagnetism
38
Slighlty attracts?
Paramagnetism
39
Strongly attracts?
Ferromagnetism
40
What's the problem with resistive magnets?
It gets weak and very hot
41
Which magnet is most expensive to buy?
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)
42
What happens if you unplug resistive magnets from the wall?
No more magnet
43
What happens if you unplug permanent magnets from the wall?
Will still have a magnet
44
Which magnet is the heaviest?
Permanent
45
Which magnet has the largest fringe field?
Superconducting
46
What are the dangers of having a strong fringe field?
- Missile or projectiles
- Tourque
47
How long do you have to wait for post op?
6-8 weeks so it can develop scar tissue
48
How do we protect the homogeneity of our main magnetic field?
Shielding
49
If its not called Faraday's cage, it could be?
RF shielding
50
What does RF shielding or Faraday's cage do?
It blocks RF from getting into the room; only shielding that stops from getting in
51
2 diff types of shielding for the flux lines?
Passive and active
52
If something is active, what can you automatically assume?
It is an electromagnet or some type of power
53
Sheets of iron or steel is what shielding?
Passive
54
How fast the hydrogen protons are spinning within the scanner is known as?
Precession
55
Why does a homogenous field matter?
To make sure they are spinning the exact same frequency
56
How do we figure out what frequency they're spinning at?
Larmor equation
57
What is larmor equation?
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
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?
For resonance
59
What is resonance?
RF pulse
60
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....
flip angle 90 degrees to transverse plane
61
More energy means what to patient?
Increase SAR
62
What is TR?
Repetition time; amount of time from one excitation pulse to the next
63
What is T1 relaxation?
Time it takes for 63% of NMV to realign with main magnet
NMV relaxes back to B0
64
Why do we have dark water on T1 weighted image?
It becomes saturated
65
What is TE?
Time from excitation RF pulse to sampling of echo signal
66
Which is shorter/faster TR or TE?
TE (page 26)
67
What is T2 relaxation?
Time it takes for 63% of transverse magnetization
68
For a T2 weighted exam, what TE do you program into the machine?
Long TR, long TE
69
Relaxation time for water?
Approx 2500 MS
70
Relaxation time for fat?
200 MS
71
******** If you want a T1 weighted image, what kind of TE do you have? ******
Short
72
If you want a T2 weighted image, what kind of TE do you have?
Long
73
TE is 100 MS, is that short or long?
Long
74
What is the worst thing we can do to our magnetic field?
Put a patient in it and it will no longer be homogenous
75
The pre scan is what?
Active shimming; evening out the field and ready for the actual scan to start
76
How is the homogenous fields measured?
- Parts per million (PPM)
- Clinical scanning is 4-10 PPM
- Spectroscopy is 1 PPM
77
What is the term for flashes of light?
Magnetophosphenes
78
Nerves are conductors
True or false?
True; walking across a magnetic field you are in motion and you will induce a current in your own nerves
79
Another name for translation?
- Projectiles
- Missiles
80
Another name for rotation?
Torque
81
Burns come from what?
B1 (RF) that burns the patient
82
What kind of EKG issues can you have?
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
The idea that moving a conductor through a magnetic field will induce a current is known as which law?
Farday
84
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?
Lenz's law; turn them sideways and that should cut across the flux lines
85
If you have an actively shielded magnet VS a non active shielded magnet, which one is more dangerous for missile effects and why?
Active shielding; stronger field when you cross the 5G line
86
Peripheral nerve stimulation is a direct result of what?
Gradient fields because they are rapidly reversing time varying magnetic fields
87
How hot can you make the patient, you can elevate their body temperature to?
1 degree celsius
88
TR is what T?
T1
89
TE is what T?
T2
90
Resonance occurs after RF pulse
True or false?
True
91
What is the term for half of an echo or the graphic illustration of your T2 decay?
FID (Free Induction Decay) ; it appears following the original excitation pulse
92
How do you obtain proton density?
Short TE, long TR (combination of T1 and T2)
93
The difference between 2 similar, but not identical tissues is known as?
Contrast resolution
94
Examples of Intrinsic? (we can't control)
- T1 recovery
- T2 decay
- Proton density
- Flow
- Diffusion
- Perfusion
95
Examples of Extrinsic? (we can control)
- TR
- TE
- Flip angle
- NSA
- Receive bandwidth
- Echo train length/turbofactor
- TI
96
Another name for bright areas of final image?
- Hyperintense
- High signal
- White
97
Another name for dark areas of final image?
- Hypointense
98
Another name for same shade of gray?
Isointense
99
Between fat and water, what has the lowest inherent energy?
Fat (short T1 relaxation time, short T2 decay)
100
A pulse sequence that begins with a 90 degree RF pulse followed by a180 degree RF pulse is known as?
Spin echo pulse sequence
101
To obtain a T1 weighted image, a _____ (short/long) TR is used to ______ (maximize/minimize) T1 effects
Short; maximize
102
To obtain a T1 weighted image, a _____ (short/long) TE is used to ______ (maximize/minimize) T2 effects
Short; minimize
103
During T2 relaxation, why would fat (or water) molecules lose coherence once the RF pulse is removed?
Because of spin spin interaction
104
Parallel and antiparallel creates?
NMV
105
Which one has the most? Parallel or antiparallel?
Parallel; otherwise we wouldn't have NMV because we can only play with parallel protons
106
What was MRI originally called and why was it changed?
Nuclear magnetic resonance; changed it because were intimated of the name after WW2
107
1 kilo hertz is how many hertz?
1,000
108
1 mega hertz is how many hertz?
1 million
109
Know SAR limits
Ch 10
110
IEC regulation limits for noise of the machine?
99 DCB
111
Is there an FDA limit for the time varying gradient fields?
No; it is what the patient can tolerate
112
Is pregnancy an issue?
- 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
