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MRI Physics - MRI 300 > Mid Term Exam > Flashcards

Mid Term Exam Flashcards

1
Q

T/F: All contrast media is potentially harmful and should be used knowledgeably.

A

True

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2
Q

T/F: Intravascular contrast media administration is performed under the supervision of a licensed physician.

A

True

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3
Q

T/F: Technical and nursing personnel injecting contrast media must be knowledgeable in the recognition of, and able to assist in the treatment of any adverse reaction.

A

True

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4
Q

T/F: Literature in the MRI community and manufacturer recommendations lists the dosage of intravenous gadolinium chelate contrast to be 0.1 mmol/kg of body weight.

A

True

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5
Q

T/F: Any and all adverse events, incidents or “near incidents” that occur pertaining to MR safety are to be reported to the MRI Medical Director, the MRI Department Supervisor or the Radiology Administrator immediately.

A

True

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6
Q

T/F: A student may review and sign the MRI screening sheet prior to an individual entering the scan room.

A

False

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7
Q

T/F: The Medical Director will be involved with the introduction of new policies and procedures as needed with the advancement of technologies and procedures in the MRI environment.

A

True

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8
Q

T/F: Zone III – This area is synonymous with the MR scanner room itself.

A

False

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9
Q

T/F: Lenz’s Law is an important consideration with non-ferromagnetic objects.

A

True

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10
Q

T/F: Having undergone a previous MRI successfully with an implanted device indicates that the device is MRI safe.

A

False

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11
Q

T/F: The potential for translational forces (“projectile forces”) exists at any field strength.

A

True

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12
Q

T/F: After a quench the patient and personnel should evacuate the area immediately.

A

True

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13
Q

Which of the following describe T1 Recovery? (Choose all that apply)

Spin lattice relaxation

The time it takes 63% of transverse magnetization to decay in the tissue.

Caused by the nuclei giving up their energy to the surrounding environment or lattice.

Spin-spin relaxation that results in decay or loss of coherent transverse magnetization.

A

Spin lattice relaxation

Caused by the nuclei giving up their energy to the surrounding environment or lattice.

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14
Q

What MUST be done prior to anyone entering the scan room? (Select the BEST answer)

Pat the patient down for metal objects.

A screening sheet must be filled out and in the patient’s chart.

The patient must be scanned with the metal detector.

The completed screening sheet must be signed by a level II staff member and the patient must be scanned with the metal detector, prior to admittance to the MRI scan room.

A

The completed screening sheet must be signed by a level II staff member and the patient must be scanned with the metal detector, prior to admittance to the MRI scan room.

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15
Q

What happens to the alignment of hydrogen protons when placed in an external magnetic field? (Check all that apply)

Nothing until an RF pulse is applied.

The magnetic moments of the nuclei align with or against the main magnetic field.

More nuclei oppose the main magnetic field than line up with the main magnetic field.

Slightly more nuclei line up with the main magnetic field than against it.

A

The magnetic moments of the nuclei align with or against the main magnetic field.

Slightly more nuclei line up with the main magnetic field than against it.

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16
Q

Where do we look up the safety of an implanted device? (Check all that apply)

www.MRISafety.com

Shellock’s reference manual

The manufacturer’s website

If we remember that it is a safe implant, there is no need to look it up again.

A

www.MRISafety.com

Shellock’s reference manual

The manufacturer’s website

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17
Q

What effect does the magneto-hemodynamic effect have? Is this a permanent effect? (Check all that apply)

Increase in the amplitude of the “R” wave on EKG gating.

Increase in the amplitude of the “T” wave on EKG gating.

Reversible effect– EKG tracing returns to normal when the patient is removed from the static magnetic field.

Permanent effect– EKG tracing continues to show an elevated wave form after the patient has had an MRI exam.

A

Increase in the amplitude of the “T” wave on EKG gating.

Reversible effect– EKG tracing returns to normal when the patient is removed from the static magnetic field.

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18
Q

What is the gyromagnetic ratio of hydrogen?

  1. 28 MHz/T
  2. 8 MHz/T
  3. 57 MHz/T
  4. 57 MHz/G
A

42.57 MHz/T

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19
Q

Select the three components of the magnetic field from those listed below.

Static Magnetic Field

Faraday’s Field

Radiofrequency Fields

Time Varying Magnetic Fields

Precessional Frequency Field

A

Static Magnetic Field

Radiofrequency Fields

Time Varying Magnetic Fields

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20
Q

What are the guidelines for pregnant employees? (Choose all that apply)

No changes to pregnant employees work environment in MRI. Everyone knows that MRI doesn’t use radiation.

Pregnant employees may enter the scan room, but should leave before scanning begins.

Pregnant employees are exempt from scanning and may only do paperwork.

Pregnant employees MUST transfer to x-ray once they’ve announced their pregnancy to the MRI department.

A

Pregnant employees may enter the scan room, but should leave before scanning begins.

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21
Q

T/F: The gyromagnetic ratio expresses the relationship between the angular momentum and the magnetic moment of each MR active nucleus.

A

True

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22
Q

Identify which of the following describe a “fringe field.” (Select all that apply)

The stray magnetic field outside the bore of the magnet.

An area on the outskirts of the magnet– generally two feet long by three feet wide.

Active or passive shielding is used to reduce the size of the fringe field.

The fringe field is not confined by walls, floors, or ceilings.

A

The stray magnetic field outside the bore of the magnet.

Active or passive shielding is used to reduce the size of the fringe field.

The fringe field is not confined by walls, floors, or ceilings.

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23
Q

What would you do in the event of a CODE BLUE in MRI? (Select all that apply)

Stay with the patient in the scan room until help arrives.

Begin CPR.

Activate the Code Blue response process (push the Code Blue button)

Get the patient out of the scanner and into Zone III; locking the scan room door and monitoring it when other Code Team members arrive

A

Begin CPR.

Activate the Code Blue response process (push the Code Blue button)

Get the patient out of the scanner and into Zone III; locking the scan room door and monitoring it when other Code Team members arrive

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24
Q

What are the two results of resonance? (Choose from the list below)

The NMV moves out of alignment and away from B0.

The NMV moves into a repeating pattern of /- 100 MHZ.

The magnetic momements of hydrogen nuclei move out of phase with each other.

The magnetic moments of hydrogen nuclei move into phase with each other.

A

The NMV moves out of alignment and away from B0.

The magnetic moments of hydrogen nuclei move into phase with each other.

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25
Q

T/F: The “warm zone” in MRI is the scan room itself.

A

False

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26
Q

Which of the following best describe spin-lattice relaxation? (Choose all that apply)

T2 Decay

T1 Recovery

Time it takes 88% of the longitudinal magnetization to recover in tissue.

Nuclei give up energy to the surrounding environment, resulting in longitudinal recovery.

A

T1 Recovery

Nuclei give up energy to the surrounding environment, resulting in longitudinal recovery.

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27
Q

What makes a nucleus an MR active nucleus? (Select all that apply)

Odd mass numbers

Atoms with a balanced mass number

Nuclei with a net spin or angular momentum

None of the above

A

Odd mass numbers

Nuclei with a net spin or angular momentum

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28
Q

T/F: We ALWAYS scan pregnant patients with contrast.

A

False

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29
Q

T/F: For resonance of hydrogen to occur, RF at EXACTLY the Larmor frequency of hydrogen must be applied.

A

True

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30
Q

What are the three types of motion present in an atom? (Select all that apply)

Electrons spinning on their own axis.

Nuclei spinning around each other.

Electrons orbiting the nucleus.

The nucleus itself spinning about its own axis.

A

Electrons spinning on their own axis.

Electrons orbiting the nucleus.

The nucleus itself spinning about its own axis.

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31
Q

Identify the two factors that determine which hydrogen nuclei align parallel and which align anti-parallel with the main magnetic field.

The strength of the external magnetic field

How many nuclei there are in each patient’s body

The thermal energy level of the nuclei

The orientation of the patient in the scanner (head first vs. feet first)

A

The strength of the external magnetic field

The thermal energy level of the nuclei

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32
Q

Which way does the main magnetic field run in permanent magnets?

Horizontally
Vertically
Side to Side
Down the bore of the magnet

A

Vertically

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33
Q

What is the terminal velocity of a paperclip at 1.5T?

64 mph
55mph
40mph
None- not attracted

A

40mph

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34
Q

Which of the following describe the purpose of gradients in MRI? (Choose all that apply)

Alter the main magnetic field in a linear fashion

Change thermal equilibrium

Spatially encode data

Cause electrons to spin on their own axis

A

Alter the main magnetic field in a linear fashion

Spatially encode data

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35
Q

What does SAR stand for?

Special Atomic Rate
Start Atoms Rolling
Specific Absorption Rate
Specific Atomic Rate

A

Specific Absorption Rate

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36
Q

What does the net magnetization vector (NMV) represent?

The type of MR active nuclei present

The relative number of electrons to protons

The atomic number of the nuclei present

The relative balance of spin-up to spin-down nuclei

A

The relative balance of spin-up to spin-down nuclei

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37
Q

Which way does the main magnetic field run in superconducting magnets?

Along the bore of the magnet (horizontal)

Along the Y-axis

Vertically

Side to side

A

Along the bore of the magnet (horizontal)

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38
Q

What is the best device to use when monitoring a patient’s status in MRI?

Blood pressure cuff

Pulse ox

EKG

Auditory monitoring

A

Pulse ox

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39
Q

What does the Larmor Equation calculate?

The NMV

The precessional frequency

The gyromagnetic ratio

The atomic mass

A

The precessional frequency

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40
Q

What is the T2 relaxation time of tissue?

[Hint: Think about which axis T2 relaxation is occurring in (longitudinal vs. transverse) and whether T2 relaxation indicates recovery vs. decay.]

The time it takes 43% of the longitudinal magnetization to recover in the tissue.

The time it takes 63% of the transverse magnetization to recover in the tissue.

The time it takes 63% of the longitudinal magnetization to decay in the tissue.

The time it takes 63% of the transverse magnetization to decay in the tissue.

A

The time it takes 63% of the transverse magnetization to decay in the tissue.

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41
Q

What is another term for T2 Decay?

Spin-lattice relaxation

Spin-spin relaxation

T1 recovery

NMV

A

Spin-spin relaxation

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42
Q

How do gradients affect the main magnetic field? (Select all that apply)

They add to the main magnetic field

They subtract from the main magnetic field

They alter the main magnetic field in a linear fashion

They give the image its shades of gray

A

They add to the main magnetic field

They subtract from the main magnetic field

They alter the main magnetic field in a linear fashion

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43
Q

T/F: Rewinders are gradients that rephase.

A

True

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44
Q

Which of the following controls T2* weighting in gradient echo?

TE
TR
Flip angle
TR and flip angle

A

TE

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45
Q

What controls the polarity of a gradient?

The steepness of the slice select gradient

The sharpness of the frequency readout

The direction of the current through the gradient coil

The strength of the main magnetic field

A

The direction of the current through the gradient coil

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46
Q

T/F: TR controls T2 weighting.

A

False

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47
Q

Which of the following is known as the basic MRI contrast?

T1 weighting
T2 weighting
Gray imaging
Proton density weighting

A

Proton density weighting

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48
Q

Choose extrinsic contrast parameters from the list below.

T1 Recovery Time
TR
Proton Density
Flip Angle
Flow
TE
b Value
A

TR
Flip Angle
TE
b Value

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49
Q

What are the two extremes of contrast in MRI?

T1 Recovery
Fat
Air
Water

A

Fat

Water

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50
Q

T/F: The TE is twice the TAU.

A

True

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51
Q

T2* decay is faster than T2 decay since it is a combination of which two of the following effects?

T1 decay with spin echo

T2 decay itself

Dephasing due to magnetic field inhomogeneities

*weighting

A

T2 decay itself

Dephasing due to magnetic field inhomogeneities

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52
Q

Which of the following best describes a T1 weighted image? (Select all that apply)

Bright water

Bright fat

Dark Water

Dark Fat

A

Bright fat

Dark Water

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53
Q

Which of the following statements is true:

Spin-spin interactions drive T1 contrast

Slow tumbling molecules lead to decreased spin-spin dephasing

Fast tumbling molecules lead to increased spin-spin dephasing

Spin-spin interactions drive T2 contrast

A

Spin-spin interactions drive T2 contrast

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54
Q

What is the approximate T1 relaxation time of water at 1T?

200 ms
500 ms
2000 ms
2500 ms

A

2500 ms

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55
Q

Which of the following items are T1 and T2 relaxation times dependent on? (hint: there are three)

How well the molecular tumbling rate matches the Larmor frequency of hydrogen

Spin-spin interactions of oxygen atoms

How closely packed the molecules are

The inherent energy of the tissue

The number of electrons orbiting the nucleus

A

How well the molecular tumbling rate matches the Larmor frequency of hydrogen

How closely packed the molecules are

The inherent energy of the tissue

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56
Q

T/F: Intrinsic parameters are those that cannot be changed because they are inherent to the body’s tissues.

A

True

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57
Q

To achieve T1 weighting in gradient echo sequences, the flip angle should be ______.

Large
Small
No flip angle should be used

A

Large

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58
Q

T/F: Spin echo sequences do not compensate for magnetic field inhomogeneities, while gradient echo sequences do compensate for magnetic field inhomogeneities.

A

False

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59
Q

___ controls the amount of T1 weighting.

TR
TE
TI
PD

A

TR

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60
Q

For PD weighting, the TR must be ______.

Long
Short
Intermediate
T1

A

Long

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61
Q

T/F: Generally speaking, gradient echo sequences are faster than spin echo sequences.

A

True

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62
Q

For T2 weighting, the TE must be _____.

short
long
intermediate
PD

A

long

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63
Q

Gradients that dephase are called __________.

rewinders

weighted

spoilers

variable flip angles

A

spoilers

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64
Q

The spin echo is created by:

The application of a long TE

The application of a rewinding gradient

A 180 degree RF pulse

A rapid TI

A

A 180 degree RF pulse

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65
Q

Gradients are used to rephase spins in gradient echo sequences because:

The resulting images have less artifact than spin echo images

They are faster to apply than an RF pulse

They rephase spins more completely than an RF pulse

They result in images with better contrast resolution

A

They are faster to apply than an RF pulse

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66
Q

Which of the following controls T1 weighting in gradient echo?

TI
TE
Gradient amplitude
TR and flip angle

A

TR and flip angle

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67
Q

Saturation results in T1 weighting because:

The flip angle used was small so vectors are not pushed beyond the transverse plane

Only occurs when the TR is long as this allows for full recovery

Vectors are pushed beyond the transverse plane because they were completely recovered before the RF excitation pulse

Vectors are pushed beyond the transverse plane as they were incompletely recovered before the RF excitation pulse

A

Vectors are pushed beyond the transverse plane as they were incompletely recovered before the RF excitation pulse

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68
Q

T/F: nhomogeneities are areas within the magnetic field that do not exactly match the external magnetic field strength.

A

True

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69
Q

What does the phase encoding gradient do?

Encode data along the LONG axis of the anatomy

Encode data along the DIAGONAL axis of the anatomy

Encode data along the SHORT axis of the anatomy

Both the DIAGONAL and SHORT axes

A

Encode data along the SHORT axis of the anatomy

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70
Q

Which gradient performs slice selection for coronal slices?

X gradient
Y gradient
Z gradient
Any combination of gradients

A

Y gradient

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71
Q

Which gradient performs phase encoding for coronal slices?

X gradient
Y gradient
Z gradient
Any combination of gradients

A

X gradient

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72
Q

When is the slice select gradient switched on during a spin echo pulse sequence?

During the rephasing pulse only

During the 90 and 180 degree pulses

During the excitation pulse only

It is always on during the scan

A

During the 90 and 180 degree pulses

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73
Q

To achieve thin slices, do we need a STEEP or SHALLOW slice select slope?

STEEP
SHALLOW

A

STEEP

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74
Q

To achieve THIN slices would we use a narrow or broad transmit bandwidth?

Narrow
Broad

A

Narrow

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75
Q

When is the phase encoding gradient switched on in a pulse sequence?

Before the 90 degree excitation pulse

Usually just before the application of the 180 degree rephasing pulse

Between TRs

During the spin echo

A

Usually just before the application of the 180 degree rephasing pulse

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76
Q

What does the slope of the frequency encoding gradient determine? (Select all that apply)

The size of the anatomy covered along the frequency encoding axis

The 180 degree rephasing pulse

The FOV

The size of the phase matrix

A

The size of the anatomy covered along the frequency encoding axis

The FOV

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77
Q

What is another term for the duration of the readout gradient?

X gradient

Sampling time

Z gradient

Window of opportunity

A

Sampling time

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78
Q

How often must we sample frequencies, according to the Nyquist Theorem?

Once per cycle
Twice per cycle
Three times per cycle
Less than once per cycle

A

Twice per cycle

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79
Q

What artifact occurs if we sample frequencies less than once per cycle?

Zipper

Cross talk

Cross excitation

Aliasing

A

Aliasing

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80
Q

What is the unit of K space?

Inches

Radians per meter

Radians per centimeter

Degrees

A

Radians per centimeter

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81
Q

T/F: The phase axis of K space is vertical and is centered in the middle of K space perpendicular to the frequency axis.

A

True

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82
Q

Which part of K space do steep phase gradients fill?

Outer lines of K space, positive only

Outer lines of K space, both positive and negative

Central lines of K space, positive only

Central lines of K space, both positive and negative

A

Outer lines of K space, both positive and negative

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83
Q

Which part of K space do shallow phase gradients fill?

Outer lines of K space, positive only

Outer lines of K space, both positive and negative

Central lines of K space, positive only

Central lines of K space, both positive and negative

A

Central lines of K space, both positive and negative

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84
Q

T/F: K space is not the image

A

True

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85
Q

Which gradient locates signal along the LONG axis of the anatomy?

Phase encoding gradient

Frequency encoding gradient

Slice select gradient

Isocenter gradient

A

Frequency encoding gradient

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86
Q

T/F: The scan time is the time to fill K space.

A

True

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87
Q

T/F: Data in K space are symmetrical.

A

True

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88
Q

What kind of information is contributed by data collected in the central lines of K space? (Select all that apply)

Resolution
Signal
Contrast
*weighting

A

Signal

Contrast

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89
Q

What kind of information is contributed by data collected in the outer lines of K space?

Resolution
Signal
Contrast
*weighting

A

Resolution

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90
Q

What controls the polarity of a gradient?

The steepness of the slice select gradient

The sharpness of the frequency readout

The direction of the current through the gradient coil

The strength of the main magnetic field

A

The direction of the current through the gradient coil

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91
Q

T/F: Phase encoding gradient positive fills the bottom half of K space.

A

False

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92
Q

Which gradient performs slice selection for sagital slices?

X gradient
Y gradient
Z gradient
Any combination of gradients

A

X gradient

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93
Q

What is another name for the frequency encoding gradient?

Phase encoding gradient
Short gradient
Readout gradient
Rephasing gradient

A

Readout gradient

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94
Q

Where are the data points collected by the system stored?

FFT
K space
Frequency domain
42.57 MHz

A

K space

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95
Q

During a typical spin echo sequence, there are three gradient applications. In chronological order they are:

Phase encoding, Slice select, Frequency encoding

Slice select, Phase encoding, Frequency encoding

Frequency encoding, Phase encoding, Slice select

Slice select, Frequency encoding, Phase encoding

A

Slice select, Phase encoding, Frequency encoding

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96
Q

Which gradient lies along the horizontal axis of a typical superconducting MRI system?

X gradient
Y gradient
Z gradient
W gradient

A

X gradient

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97
Q

If a 512 phase matrix is selected, which k-space lines are likely to be filled in a normal acquisition?

0 to 512

256 to -256

0 to -512

256, 0 to -255

A

256 to -256

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98
Q

Which of the following statements is true?

A data point contains frequency encoding information only

A data point contains phase encoding information only

A data point contains both phase and frequency information

A data point represents a specific pixel on the image

A

A data point contains both phase and frequency information

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99
Q

T/F: A thicker slice has a better SNR than a thinner slice.

A

True

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100
Q

Decreasing receive bandwidth by half increases the SNR by how much?

60%

40%

1/2

.22

A

40%

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101
Q

T/F: A fine matrix is one with a low number of frequency encodings and/or phase encodings, and results in a small number of pixels in the FOV.

A

False

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102
Q

Choose three factors that affect the SNR from the list below (there are three factors).

Magnetic field strength of the system

Proton density of the area under examination

The patient’s height and weight

Receive bandwidth

A

Magnetic field strength of the system

Proton density of the area under examination

Receive bandwidth

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103
Q

T/F: A long TE increases SNR and a short TE decreases SNR.

A

False

104
Q

T/F: TR controls the amount of T2 weighting.

A

False

105
Q

Choose the term that best describes “a unit volume of patient tissue” from the list below.

Pixel

Grayscale value

Voxel

Slice thickness

A

Voxel

106
Q

Which of the following factors affect scan time during a sequential acquisition? (choose all that apply)

TR
TE
Phase Matrix
NEX
Frequency Matrix
A

TR
Phase Matrix
NEX

107
Q

Which of the following factors affect voxel size (choose all that apply)?

Slice thickness

Number of pixels or matrix

Size of the flip angle

FOV

A

Slice thickness

Number of pixels or matrix

FOV

108
Q

T/F: Square pixels ALWAYS provide better spatial resolution than rectangular pixels.

A

True

109
Q

If we double the NEX, what does that do to our scan time?

Reduces the scan time by 1/2

Doubles the scan time

Reduces the scan time by 1.4

Increases the scan time by 1.4

A

Doubles the scan time

110
Q

Decreasing the phase matrix does which of the following?

Decreases SNR

Increases spatial resolution

Makes the scan shorter

Has no effect on scanning

A

Makes the scan shorter

111
Q

Of the following parameters, which would give the best spatial resolution?

256 × 256, 3 mm slice thickness, 12 cm FOV, 1 NEX

256 × 128, 8 mm slice thickness, 40 cm FOV, 4 NEX

512 × 256, 6 mm slice thickness, 14 cm FOV, 2 NEX

None of the above would give good spatial resolution.

A

256 × 256, 3 mm slice thickness, 12 cm FOV, 1 NEX

112
Q

Of the following parameters, which would give the highest SNR?

256 × 256, 3 mm slice thickness, 12 cm FOV, 1 NEX

256 × 128, 8 mm slice thickness, 40 cm FOV, 4 NEX

512 × 256, 6 mm slice thickness, 14 cm FOV, 2 NEX

None of the above.

A

256 × 128, 8 mm slice thickness, 40 cm FOV, 4 NEX

113
Q

Increasing the field strength increases SNR because:

The flip angle increases

The NMV increases in size because the high energy population of spins increases

The precessional frequency increases

The NMV increases in size because the low energy population of spins increases

A

The NMV increases in size because the low energy population of spins increases

114
Q

Halving a square FOV reduces the SNR by:

1/2
1/4
3/4
1/8

A

3/4

115
Q

Which of the following does NOT occur when the receive bandwidth is reduced?

SNR increases

Chemical shift artifact improves

Number of slices available decreases

TE increases

A

Chemical shift artifact improves

116
Q

Doubling the number of signal averages changes the SNR by how much?

× 2
1/2
22
√2

A

√2

117
Q

Which of these is a consequence of decreasing the TR from 2500 ms to 500 ms?

Scan time decreases

T1 weighting decreases

Spatial resolution decreases

Slice number available increases

A

Scan time decreases

118
Q

Do we achieve greater SNR with a long or a short TR?

long
short

A

long

119
Q

Pixel area = __ / matrix size.

SNR
Resolution
FOV
GNR

A

FOV

120
Q

Which sequence is considered the gold standard for MR imaging?

SSFP
Spin Echo
Gradient Echo
Coherent Gradient Echo

A

Spin Echo

121
Q

What is the approximate T1 relaxation time of CSF at 1T?

2000 ms
150 ms
500 ms
3000 ms

A

2000 ms

122
Q

What is the approximate T1 relaxation time of fat at 1T?

2000 ms
200 ms
500 ms
3000 ms

A

200 ms

123
Q

What do T1 images typically best demonstrate?

Anatomy
Pathology
Bright fluid
Everything

A

Anatomy

124
Q

What does STIR stand for? Short ___ Inversion Recovery.

A

Tau
tau
TAU

125
Q

When would we be most likely to use a STIR sequence?

CSF flow studies

MSK studies (i.e. knee, wrist)

Head or Spine studies (to look for periventricular lesions)

All studies must include a STIR sequence

A

MSK studies (i.e. knee, wrist)

126
Q

T/F: FLAIR stands for Fluid Low Attenuation Inversion Recovery

A

False

127
Q

When would we be most likely to use a FLAIR sequence?

MSK studies (i.e. knee, wrist)

Head or spine studies (to look for periventricular lesions)

All studies must include a FLAIR sequence

To image the great vessels

A

Head or spine studies (to look for periventricular lesions)

128
Q

How is time reduced in fast spin echo? (Choose all that apply)

The operator must prescribe fewer slices

Use a turbo factor

Use thinner slices

Use an echo train

A

Use a turbo factor

Use an echo train

129
Q

What artifact can occur as a result of using long echo trains?

Cross talk
Truncation
Image Blurring
Aliasing

A

Image Blurring

130
Q

An inversion recovery pulse sequence begins with which of the following?

90 degree RF pulse

180 degree inverting pulse

180 rephasing pulse

Gradient pulse (variable flip angle)

A

180 degree inverting pulse

131
Q

Which Fast Inversion Recovery sequence(s) do we often use?

STIR
SSFP
FLAIR
Incoherent Gradient Echo

A

STIR

FLAIR

132
Q

What is Double IR prep used to accomplish?

Used to null blood for cardiac imaging

Flips the NMV back to zero

Imaging large patients

FSE sequences

A

Used to null blood for cardiac imaging

133
Q

A coherent gradient echo sequence samples which of the following?

FID Only

Stimulated Echo Only

Both the FID and Stimulated Echo

T2 Information Only

A

Both the FID and Stimulated Echo

134
Q

T/F: During EPI all the lines of K space are filled during one repetition.

A

True

135
Q

How is K space filled in Fast Gradient Echo Sequences? (choose all that apply)

Elliptical filling
Centric filling
Keyhole filling
Outside to inside

A

Centric filling

Keyhole filling

136
Q

In which of the following sequences is all the transverse magnetization rewound at the end of each TR period?

Coherent gradient echo
Incoherent gradient echo
EPI

A

Coherent gradient echo

137
Q

Which of the following statements is true in an incoherent gradient echo sequence?

Residual transverse magnetization has the same phase as the magnetization most recently created

The flip angle is always 10°

The system discriminates between residual and the most recently created transverse magnetization because it has a different phase value

It is not a steady state sequence

A

The system discriminates between residual and the most recently created transverse magnetization because it has a different phase value

138
Q

What type of echoes are sampled during SS-FSE?

Spin echoes
Gradient echoes
Incoherent Gradient echoes

A

Spin echoes

139
Q

What are the advantages of propeller K Space filling?

Better detail

Low SNR but high resolution

Bright signal

Rapid imaging, increased SNR and CNR, reduced motion artifact.

A

Rapid imaging, increased SNR and CNR, reduced motion artifact.

140
Q

T/F: Using a long echo train decreases the SAR.

A

False

141
Q

T/F: STIR sequences should NOT be used in conjunction with contrast enhancement.

A

True

142
Q

T/F: Spin echo pulse sequences are classified according to whether the residual transverse magnetization is in phase (coherent) or out of phase (incoherent).

A

False

143
Q

SSFP sequences usually produce images that are ___ weighted.

T1
T2
T2*
T1 or T2*

A

T2

144
Q

T/F: Parallel imaging is usually used to increase resolution or decrease scan time.

A

True

145
Q

Which artifact is produced as a result of motion of flowing nuclei?

Zipper effect

Aliasing

Phase ghosting

Truncation

A

Phase ghosting

146
Q

Which type of motion can we compensate for in MRI?

First order laminar flow

Second order motion acceleration

Third order motion jerk

All of those listed can be compensated for

A

First order laminar flow

147
Q

T/F: TOF phenomenon results in a dark vessel.

A

True

148
Q

Which of the following effects does TOF depend on? (Select all that apply)

Velocity of flow
TE
Slice Thickness
TR

A

Velocity of flow
TE
Slice Thickness

149
Q

Choose the two main uses of spatial pre-saturation from the list below. (Select all that apply)

Chemical Pre-saturation
STIR
FLAIR
SPIR

A

Chemical Pre-saturation

SPIR

150
Q

T/F: Counter current flow occurs when flowing nuclei are traveling in the same direction as slice selection.

A

False

151
Q

Which of the following is/are result(s) of time of flight? (Select all that apply)

Flow-related enhancement

Entry slice phenomenon

High velocity signal void

Zipper effect

A

Flow-related enhancement

High velocity signal void

152
Q

In a dual echo sequence, which of the following combinations would result in reduced flow artifact in the second echo?

TE 20 and 50 ms
TE 20 and 70 ms
TE 40 and 80 ms
TE 40 and 95 ms

A

TE 40 and 80 ms

153
Q

What is the chemical shift at 1.5 T?

2.2 Hz
22 Hz
220 Hz
220KHz

A

220Hz

154
Q

T/F: STIR is most useful in post contrast imaging.

A

False

155
Q

T/F: Even echo rephasing reduces intra-voxel dephasing.

A

True

156
Q

T/F: Intra-voxel dephasing results in an increase in total signal amplitude from the voxel.

A

False

157
Q

Stationary nuclei always receive both excitation and rephasing pulses, but flowing nuclei present in the slice for the excitation may have exited the slice before rephasing. This is called ______________.

Time of Flight Phenomenon

Entry Slice Phenomenon

Intra-Voxel Dephasing

Turbulent Flow Effects

A

Time of Flight Phenomenon

158
Q

T/F: As velocity of flow decreases, the time of flight effect decreases.

A

True

159
Q

T/F: Another term for time of flight is inflow effect.

A

False

160
Q

Determine which of the following parameters would result in the most entry slice phenomenon (i.e. entry slice phenomenon would increase compared to the other options).

Slice 1 of 20, 3000 TR, .7 mm slice thickness

Slice 1 out of 20, 400 TR, 1.2 mm slice thickness

Slice 10 out of 20, 3000 TR, 1.2 mm slice thickness

Slice 10 out of 20, 400 TR, .7 mm slice thickness

A

Slice 1 of 20, 3000 TR, .7 mm slice thickness

161
Q

T/F: Flow affects image quality.

A

True

162
Q

The frequency difference between fat and water is called ___________ and can be used to specifically null the signal from either fat or water.

Chemical Pre-Saturation
Chemical Shift
Precessional Frequency
Even Echo Rephasing

A

Chemical Shift

163
Q

T/F: Any tissue can be nulled as long as an RF pulse matching its precessional frequency is applied to the imaging volume before excitation.

A

True

164
Q

T/F: Pre-saturation techniques increase the RF deposition to the patient.

A

True

165
Q

What is another term for phase ghosting?

Phase wrap

Phase mismapping

Chemical misregistraion

Aliasing

A

Phase mismapping

166
Q

What is another term for phase ghosting?

Phase wrap

Phase mismapping

Chemical misregistraion

Aliasing

A

Phase mismapping

167
Q

In which direction does phase ghosting occur? (Choose all applicable)

Phase Axis

Frequency Axis

Slice Select Axis

Anterior to Posterior

A

Phase Axis

168
Q

Which of the following are methods of reducing phase ghosting? (Choose all that apply)

Using respiratory compensation techniques

Decrease the TE

Carefully explain the procedure to the patient

Swap phase and frequency

Use pre-saturation pulses

Use “no phase wrap” software

A

Using respiratory compensation techniques

Carefully explain the procedure to the patient

Swap phase and frequency

Use pre-saturation pulses

169
Q

In which direction does aliasing occur? (Choose all that apply)

Phase Axis

Frequency Axis

Slice Select Axis

Anterior to Posterior

A

Phase Axis

Frequency Axis

170
Q

Which of the following is a remedy for aliasing?

Decreasing the slice thickness

Decreasing the size of the FOV

Decreasing the TE

Using “no phase wrap” software

A

Using “no phase wrap” software

171
Q

Which of the following best describes the appearance of chemical shift artifact on an image?

Extra information wraps into the image

The cancellation of fat and water signals when they are out of phase.

Banding artifact at the interfaces of high and low signal.

Produces a dark edge at the interface between fat and water.

A

Produces a dark edge at the interface between fat and water.

172
Q

In which direction does chemical shift artifact occur? (Choose all that apply)

Phase Axis

Frequency Axis

Slice Select Axis

Anterior to Posterior

A

Frequency Axis

173
Q

What unit is used to express the amount of chemical shift?

MHz

Hz

ppm

gyromagnetic ratio

A

ppm

174
Q

What is another name for a truncation artifact in a sagital cervical spine?

Truncation

Gyromagnetic Artifact

Gibbs

Faraday

A

Gibbs

175
Q

How can we reduce truncation?

Increase the TE

Increase the TR

Increase the number of phase encoding steps

Increase the number of frequency encoding steps

A

Increase the number of phase encoding steps

176
Q

In which direction does truncation occur? (Choose all that apply)

Phase Axis

Frequency Axis

Slice Select Axis

Anterior to Posterior

A

Phase Axis

177
Q

Which best describes the appearance of a zipper artifact?

Distortion of the image together with large signal voids.

Anatomy folded into the FOV

A dense line on the image at a specific point.

Tissues return a high signal intensity

A

A dense line on the image at a specific point.

178
Q

Which best describes the appearance of a zipper artifact?

Distortion of the image together with large signal voids.

Anatomy folded into the FOV

A dense line on the image at a specific point.

Tissues return a high signal intensity

A

A dense line on the image at a specific point.

179
Q

Which of the following is a possible cause of shading artifact?

A hemorrhage

A leak in the RF shielding of the scan room

Spin echo sequences

Inhomogeneities in the main magnetic field

A

Inhomogeneities in the main magnetic field

180
Q

Which of the following best describes Moire artifact?

Black and white banding artifact on the edge of the FOV

Fat and water are out of phase and their signals cancel each other out.

Different chemical environments of fat and water produce a dark edge at the interface between fat and water.

Anatomy from outside the FOV are wrapped into the image.

A

Black and white banding artifact on the edge of the FOV

181
Q

T/F: To reduce chemical shift artifact, ALWAYS use the widest receive bandwidth in keeping with good SNR and the smallest FOV possible.

A

True

182
Q

T/F: To reduce chemical shift artifact, ALWAYS use the widest receive bandwidth in keeping with good SNR and the smallest FOV possible.

A

True

183
Q

In spin echo sequences using a pre-saturation pulse, what would persistent bright signal within the vessel indicate?

Slow Flowing Blood

Fast Flowing Blood

Blood Clot

Vascular Occlusion

A

Slow Flowing Blood

Blood Clot

Vascular Occlusion

184
Q

Which of the following best describes what the “P” wave represents?

Atrial Systole (Contraction)

Ventricular Systole

Ventricular Diastole

None of the above

A

Atrial Systole (Contraction)

185
Q

Which of the following best describes what the “QRS” complex represents?

Atrial Systole (Contraction)

Ventricular Systole

Ventricular Diastole (Relaxation)

None of the above

A

Ventricular Systole

186
Q

Which of the following best describes what the “T” wave represents?

Atrial Systole (Contraction)

Ventricular Systole

Ventricular Diastole (Relaxation)

None of the above

A

Ventricular Diastole (Relaxation)

187
Q

Which of the following sequence(s)/technique(s) can be used to make vessels appear bright?

Gradient Echo Imaging

Gradient Moment Rephasing

Contrast Enhancement

All of the above

A

All of the above

188
Q

Which of the following is used to trigger each pulse sequence when using ECG gating?

P wave

Q wave

R wave

S wave

A

R wave

189
Q

How much does a typical patient’s heart rate vary during an exam?

10- 20 %

20- 30%

40- 50%

60- 70%

A

10- 20 %

190
Q

If the R to R interval is 500 ms, the trigger window is 10%, and the trigger delay is 50 ms, what is the time available to acquire data?

310 ms

400 ms

460 ms

500 ms

A

400 ms

191
Q

If the R to R interval is 500 ms, the trigger window is 10%, and the trigger delay is 50 ms, what is the time available to acquire data?

310 ms

400 ms

460 ms

500 ms

A

400 ms

192
Q

What determines the length of the R to R interval?

The technologist performing the exam

The radiologist who establishes the protocol

The patient’s heart rate

The type of sequence

A

The patient’s heart rate

193
Q

What is the waiting period before each R wave called?

Trigger Window

Trigger Delay

R to R Interval

Available Imaging Time

A

Trigger Window

194
Q

T/F: ECG gating is prospective.

A

True

195
Q

When using MRA to evaluate intracranial vascularity, flow within smaller vessels can best be demonstrated by:

2D Time of Flight MRA

3D Time of Flight MRA

3D Phase Contrast MRA

All of the Above

A

3D Time of Flight MRA

196
Q

When using MRA to evaluate intracranial vascularity, flow within smaller vessels can best be demonstrated by:

2D Time of Flight MRA

3D Time of Flight MRA

3D Phase Contrast MRA

All of the Above

A

3D Time of Flight MRA

197
Q

MRA techniques include all of the following EXCEPT:

TOF-MRA

PC-MRA

CE-MRA

CT-MRA

A

CT-MRA

198
Q

Which of the following does NOT reduce flow motion artifact?

SAT

ECG gating

GMN

Subtraction

A

Subtraction

199
Q

Which of the following can be used to improve coverage and at the same time maintain the signal from blood flowing within the larger volume?

MC-TOF

PC-MRA

MOTSA

Phase images

A

MOTSA

200
Q

The vascular signal, produced on time of flight MRA (TOF-MRA), relies on:

MOTA

PC

Flow related enhancement

Velocity-induced phase shifts

A

Flow related enhancement

201
Q

The vascular signal, produced on PC-MRA, relies on:

MOTA

PC

Flow related enhancement

Velocity-induced phase shifts

A

Velocity-induced phase shifts

202
Q

Contrast enhanced MRAs are acquired with all of the following EXCEPT:

Test bolus

Bolus tracking

VENC settings

Fluoro triggering

A

VENC settings

203
Q

Contrast enhanced MRAs are acquired with all of the following EXCEPT:

Test bolus

Bolus tracking

VENC settings

Fluoro triggering

A

VENC settings

204
Q

Multiphase images, acquired with additional modulation of magnetization, are known as:

TOF-MRA

PC-MRA

VENC

SPAMM

A

SPAMM

205
Q

What is the available imaging time using these parameters? R to R 800 ms, trigger window 10%, delay after trigger 4 ms.

688 ms

700 ms

716 ms

800 ms

A

716 ms

206
Q

When using MRA to evaluate peripheral vascular flow, such as that within the arteries of the legs, saturation pulses are:

Placed superior to the acquired slices

Placed in the acquired slices

Placed inferior to the acquired slices

Not necessary

A

Placed inferior to the acquired slices

207
Q

When using MRA to evaluate extracranial vascular flow, such as that within common carotid arteries, a recommended technique is:

2D time of flight MRA

3D time of flight MRA

3D phase contrast MRA

All of the above

A

2D time of flight MRA

208
Q

When using MRA to evaluate extracranial vascular flow, such as that within common carotid arteries, a recommended technique is:

2D time of flight MRA

3D time of flight MRA

3D phase contrast MRA

All of the above

A

2D time of flight MRA

209
Q

Magnetic field strength can be expressed in units of Tesla (T) or gauss (G), where:

1 T = 1 G

  1. 5 T = 1500 G
  2. 0 T = 0.3 G

1 T = 10 000 G

A

1 T = 10 000 G

210
Q

The homogeneity of a magnetic field is expressed in units of:

ppm (parts per million)

T (Tesla)

G (gauss)

MHz (megaHertz)

A

ppm (parts per million)

211
Q

The homogeneity of a magnetic field is expressed in units of:

ppm (parts per million)

T (Tesla)

G (gauss)

MHz (megaHertz)

A

ppm (parts per million)

212
Q

Gradient strength is expressed in units of all of the following EXCEPT:

w/kg

mT/m

G/cm

T/m/s

A

w/kg

213
Q

Gradient strength is expressed in units of all of the following EXCEPT:

w/kg

mT/m

G/cm

T/m/s

A

w/kg

214
Q

Passive magnetic shielding can be accomplished by lining the scan room walls with:

Copper

Lead

Steel

Shim plates

A

Steel

215
Q

Fourier transform (FT) is a mathematical process that is used to convert MR signal from a FID into a spectrum. FT occurs in the:

Image processor

Array processor

RF coil

Gradient amplifier

A

Array processor

216
Q

What rule determines the direction of current flow through a coil, and the direction of the magnetic field that the current produces?

The size of the magnetic field

Right hand thumb rule

MRI Fringe Field Rule

Whether you are using an open or closed configuration

A

Right hand thumb rule

217
Q

What is the maximum field strength allowed for clinical imaging of adults in the USA?

3 T

4 T

8 T

10 T

A

8 T

218
Q

T/F: The purpose of magnetic field shimming is to reduce the size of the fringe field.

A

False

219
Q

What is the most common material used to make permanent magnets?

Titanium

Helium

Iron

Alnico

A

Alnico

220
Q

Ohm’s law states:

B = k (l)

V = I (R)

B = H (1 x)

1 T = 10 kG

A

V = I (R)

221
Q

T/F: The law of electromagnetic induction indicates that whenever a charge particle such as an electron exhibits motion, a corresponding magnetic field is induced.

A

True

222
Q

Which cryogen is commonly used to super cool wires in MRI?

Liquid helium

Niobium

Alnico

Hydrogen

A

Liquid helium

223
Q

Which material is most commonly used to make superconducting wires?

Liquid helium

Niobium-titanium alloy

Alnico

Hydrogen

A

Niobium-titanium alloy

224
Q

Why do we use shimming?

To apply a magnetic field

To make the field even or homogenous

To make the magnetic field smaller

To induce a current

A

To make the field even or homogenous

225
Q

Select all of the following that determine the strength of an electromagnet:

The amount of current passed through the windings

The number of windings in the coil

The distance or spacing between the windings

The diameter of the wire used in the windings

A

All of the above

226
Q

In a typical superconducting magnet, the direction of the magnetic field is:

Vertical

Horizontal

Around the flux lines

Hard to measure

A

Horizontal

227
Q

T/F: The SNR is enhanced when using local coils.

A

True

228
Q

T/F: The SNR is enhanced when using local coils.

A

True

229
Q

What does BOLD stand for?

Blood oxygenation level dependent

Blood oxygen line developed

Body oriented level dependent

Type of CT scanning

A

Blood oxygenation level dependent

230
Q

Functional imaging techniques include which of the following (check all that apply)?

DWI

fMRI

Spectroscopy

Perfusion imaging

A

All of the above

231
Q

T/F: Functional imaging techniques allow MRI to be used to assess function and physiology as opposed to merely conventional structural imaging.

A

True

232
Q

What term is used to describe the net displacement of diffusion spins across a tissue?

SWI

fMRI

ADC

MRS

A

ADC

233
Q

What is the extrinsic parameter that controls the amount of diffusion seen in an image?

TR

TE

flip angle

b factor

A

b factor

234
Q

What signal intensity is an area of abnormality likely to have on an ADC map?

Hypointense

Hyperintense

Isointense

A

Hypointense

235
Q

What signal intensity is an area of abnormality likely to have on a trace image?

Hypointense

Hyperintense

Isointense

A

Hyperintense

236
Q

T/F: Perfusion is the regional blood flow in tissues and is defined as the volume of blood that flows into one gram of tissue.

A

True

237
Q

Which of the following best describes a use for MR Spectroscopy (MRS)?

To show ankle anatomy

To aid in brain tumor staging

To demonstrate perfusion

A

To aid in brain tumor staging

238
Q

T/F: Interventional MRI includes performing biopsies in the MR suite.

A

True

239
Q

Chemical shift is measured in which of the following units?

mm/s

ppm

T/m

G/cm

A

ppm

240
Q

T/F: Perfusion is measured using MRI by tagging the fat in arterial blood during image acquisition.

A

False

241
Q

The anatomy of white matter tracts can be mapped using strong multi-directional gradients in which of the following?

SWI

diffusion tensor imaging (DTI)

continuous arterial spin labeling (CASL)

CBV

A

diffusion tensor imaging (DTI)

242
Q

T/F: MR microscopy (MRM) is useful as a research tool when studying detail in a very small area of tissue.

A

True

243
Q

T/F: MR microscopy (MRM) is useful as a research tool when studying detail in a very small area of tissue.

A

True

244
Q

T/F: Gadolinium chelates are ferromagnetic.

A

False

245
Q

After gadolinium administration, it is recommended that which images are acquired?

One T1 weighted image

One T2 weighted image

Multiple T1 weighted images

Multiple T2 weighted images

A

Multiple T1 weighted images

246
Q

Enhanced MR images are evaluated for sensitivity and specificity, where sensitivity is ________ and specificity is ________.

The ability to detect the lesion/the ability to classify the lesion

The ability to classify the lesion/the ability to detect the lesion

TE used to evaluate the lesion/TR used to evaluate the lesion

TR used to evaluate the lesion/TE used to evaluate the lesion

A

The ability to detect the lesion/the ability to classify the lesion

247
Q

T/F: All gadolinium contrast agents have the same ‘relaxivity’.

A

False

248
Q

Choose all of the following that enhancement agents can be useful in detecting.

Infection

Tumors

Infarction

Inflammation

A

All of the above

249
Q

On a T1 weighted pre-contrast image, fat appears _____ and water appears _____.

Bright, Dark

Bright, Bright

Dark, Bright

Dark, Dark

A

Bright, Dark

250
Q

T/F: Scar tissue enhances in the lumbar spine shortly after the injection of contrast.

A

True

251
Q

T/F: Scar tissue enhances in the lumbar spine shortly after the injection of contrast.

A

True

252
Q

Which sequence would be used to best visualize metastatic lesions in the bone?

FLAIR with contrast

Fat saturation techniques with contrast

T2 weighted sequences

Non-contrast imaging

A

Fat saturation techniques with contrast

253
Q

T/F: Gadolinium cannot cross the intact blood-brain barrier (BBB).

A

True

254
Q

Gadolinium element is ________ and gadolinium chelate contrast media is ________.

Ferromagnetic/paramagnetic

Ferromagnetic/ferromagnetic

Paramagnetic/ferromagnetic

Paramagnetic/paramagnetic

A

Ferromagnetic/paramagnetic

255
Q

T/F: When using gadolinium, the T1 relaxation time of the water is reduced so enhancing lesions (such as tumors associated with free water) appear bright on a T1 weighted image.

A

True

256
Q

Select all of the following that were discussed as possible MR contrast agents in the text.

Gadolinium

Blueberry juice

Mango juice

Dilute barium solutions

A

All of the above

MRI Physics - MRI 300 (1 decks)

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