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MRI > MRI Physics 1 > Flashcards

MRI Physics 1 Flashcards

0
Q 
If a voltage V drives a current I through a resistance R, then the value of the current is given by Ohm's Law:
A. I= VxR
B. I = R/V
C. I = V/R
D. None of the above
A

C. I = V/R

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1
Q 
Hydrogen makes up approximately what percentage of all atoms in the human body?
A. 20
B. 40
C. 80
D. 100
A

C. 80%

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2
Q 
If the static magnetic field is .3T, what is the larmor precession frequency of the hydrogen proton spins?
A. 12.8 MHz
B. 42.6 MHz
C. 63.9 MHz
D. 63.9 Hz
A

A. 12.8 MHz

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3
Q

Hydrogen nuclei have a magnetic moment because they have which properties?
I. Spin
II. Charge
III. Relaxation time

A. I only
B. II only
C. I and II only
D. I II and III

A

C. I and II only

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4
Q 
About how many times stronger is the static magnetic field from a 1.0T MRI scanner than the earths magnetic field at the surface of the planet?
A. 2 times
B. 20 times
C. 200 times
D. 20,000 times
A

D. 20,000 times

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5
Q 
Net magnetization is a vector.  Vectors have both:
A. Spin and charge
B. mass and charge
C. Magnitude and direction
D. Mass and direction
A

C. Magnitude and direction

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6
Q 
By MRI convention the equilibrium magnetization is represented by:
A. B0
B. B1
C. M0
D. Mz
A

C. M0

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7
Q

The t1 relaxation time is defined as when
A. 37% of the longitudinal magnetization has recovered
B. 63% of the longitudinal magnetization has recovered
C. 63% of the transverse magnetization has recovered
D. 37% of the transverse magnetization has recovered

A

B. 63% of the longitudinal magnetization has recovered

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8
Q 
The rate of decay of an FID is given by
A. T1
B. T1*
C. T2
D. T2*
A

D. T2*

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9
Q 
A long TR
A. Increases T1 weighting
B. decreases T1 weighting
C. Increases T2 weighting
D. Decreases T2 weighting
A

B. decreases T1 weighting

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10
Q 
Which of the following are active MR nuclei?
I. C12
II. C13
III. Na22
IV. Na23

A. I and III
B. II and IV
C. III and IV
D. I II III and IV

A

B. II and IV

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11
Q 
For spin echo imaging what type of contrast will TR 2500ms and TE 150ms produce?
A. T1
B. T2
C. T2*
D. PD
A

B. T2

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12
Q 
Spins aligned in the anti parallel direction are in a 
A. Low energy state
B. high energy state
C. Resonant state
D. Flux state
A

B. high energy state

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13
Q 
The cause of transverse magnetization Mxy dephasing is?
A. Spin lattice interaction
B. spin spin interaction 
C. Magnetic inhomogeneities
D. B and C
A

D. B and C

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14
Q 
Spin density is another term for
A. Nuclear density
B. hydrogen density
C. Proton density
D. B and C
A

D. B and C

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15
Q 
For resonance, the B1 field oscillates at what frequency?
A. ω0 = γΒ0
Β. ω1 = γΒ1
C. ω = γ(Β+\-ΔΒ)
D. None of the above
A

A. ω=γΒ0

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16
Q 
T2* is a result of dephasing due to a tissues T2 time and 
A. T1
B. magnetic inhomogeneities 
C. Molecular weight
D. A and B
A

B. magnetic inhomogeneities

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17
Q 
Suppose the longitudinal magnetization Mz = M0 is flipped into the transverse plane.  Then the initial value for the transverse magnetization is Mxy = M0. Thus during the RF pulse, the spins system is said to have what property?
A. T1
B. T2
C. Coherence
D. Incoherence
A

C. Coherence

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18
Q 
The MRI process leading to a voltage or electric current being induced in the receiver coil can be explained by
A. Faradays law
B. Coulomb's law 
C. Ohms law
D. Newtons law
A

A. Faradays law

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19
Q 
What is the time between two successive RF excitation pulses called
A. Tau
B. TE
C. TR
D. T1
A

C. TR

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20
Q 
Radio waved travel at what speed?
A. Speed of sound
B. speed of light
C. 3x10^8 m/s
D. B and C
A

D. B and C

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21
Q

The law for the force F between two electric stationary charges q and Q separated by a distance d is
F = kqQ/d^2

Where k is a constant. This force law is also called?
A. Faraday's law
B. ohms law
C. Coulomb's law 
D. Newtons law
A

C. Coulomb’s law

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22
Q 
At what flip angle is maximum transverse magnetization obtained?
A. 45°
B. 90°
C. 180°
D. Depends on the imaging sequence
A

B. 90°

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23
Q

Images acquired using a long TE time may result in which of the following image quality results?
I. Lower SNR
II. higher image graininess
III. Lower T2 contrast

A. I only
B. II Only
C. I and II only
D. I II and III

A

C. I and II

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24
Q 
To calculate the precession frequency, the strength of the magnetic field is multiplied by a constant known as
A. The resonance factor
B. The gyro magnetic ratio
C. The linear attenuation coefficient
D. Planck's constant
A

B. the gyro magnetic ratio

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25
Q 
The MR signal is produced by magnetization
A. In the longitudinal direction
B. in the transverse plane 
C. Out of phase
D. A and B
A

B. in the transverse plane

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26
Q 
Magnetic susceptibility effects are seen most prominent in which pulse sequences below
A. IR
B. CSE
C. GRE
D. FSE
A

C. GRE

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27
Q 
Following a 90° RF pulse, the MRI signal that is created is called
A. Spin echo
B. FRE
C. Free induction decay
D. B and C
A

C. Free induction decay

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28
Q 
On a t2 weighted image, what is the typical range for allowed TR?
A. 200-700ms
B. 500-700ms
C. 2000 ms or greater
D. Any TR value is allowed
A

C. 2000 ms or greater

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29
Q 
On a spin echo pulse sequence, what does the tau time equal?
A. τ=TR
B. τ=TR/2
C. τ=TE
D. τ= TE/2
A

D. τ= TE/2

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30
Q 
In conventional dual SE pulse sequences using a long TR, what type of contrast is usually acquired?
A. T2 1st, T2 2nd
B. T1 1st, PD 2nd
C. PD 1st, T2* 2nd
D. PD 1st, T2 2nd
A

D. PD 1st T 2 2nd

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31
Q 
What is the precessional frequency necessary to excite hydrogen protons exposed to a 1.9T magnetic field?
A. 63.9mHz
B. 63.9 MHz
C. 80.9 MHz
D. 80.9 mHz
A

C. 80.9 MHz

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32
Q 
Which pulse sequence usually converts only a portion of the longitudinal magnetization into transverse magnetization?
A. IR
B. SE
C. FSE
D. GRE
A

D. GRE

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33
Q 
A typical time duration for an RF pulse might be?
A. 500ms
B. 500μs
C. .5ms
D. B and C
A

D. B and C

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34
Q 
At static fields near 3T what will happen to the T1 of a tissue compared to the tissue T1 at static field near 1.5T?
A. T1 decreases
B. T1 increases
C. T1 unaffected
D. A or B depending on the tissue
A

B. T1 increases

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35
Q 
In relation to the static magnetic field the B1 magnetic field is oriented
A. Parallel
B. perpendicular
C. At 180°
D. At 45°
A

B. perpendicular

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36
Q 
What is the decay rate for an FID?
A. R1
B. R2
C. R2*
D. None of the above
A

C. R2*

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37
Q 
In a spin echo pulse sequence, the initial 90° RF pulse is for \_\_\_\_\_\_\_\_ of spins
A. Longitudinal alignment
B. spin equilibrium
C. Excitation 
D. Refocusing of inhomogeneities
A

C. Excitation

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38
Q 
Which frequencies must be the same for resonance to occur on MRI
A. RF and precession
B. RF and larmor
C. Precession and Larmor
D. A and B
A

D. A and B

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39
Q 
Which of the following tissues has the longest T 2 decay time?
A. CSF 
B. white matter
C. Gray matter
D. Fat
A

A. CSF

40
Q

Put the following wavelengths in order from smallest to largest

X-rays radio waves and microwaves

A

Radiowaves, microwaves, x-rays

41
Q 
How many energy states does a spin 3/2 nucleus have in a static magnetic field B0
A. 2
B. 3
C.4
D.5
A

C. 4

42
Q 
Which of the following is true?
A. Fat T1>water T1 , fat T2> water T2
B. fat T1> water T1, water T2> fat T2
C. Fat T1< water T1, Fat T2> water T2
D. Fat T1< water T1, water T2> fat T2
A

D. Fat T1< water T1 Water T2> Fat T2

43
Q 
The atomic number of an atom is
A. Number of protons
B. number of protons plus neutrons
C. Number of protons minus neutrons 
D. None of the above
A

A. Number of protons

44
Q

Which of the following nuclei are MRI active?
I. H1
II. O16
III. F19

A. I and II
B. I and II
C. II only
D. I II and III

A

B. I and II

45
Q 
On a dual echo SE pulse sequence for the brain with long TR and TE1<TE2 for which image contrast would the CSF signal look the brightest?
A. T1
B. T2
C. PD
D. All of the above
A

B. T2

46
Q 
About how many hydrogen proton spins are there in a 1mm^3 vowel of fat 
A. < 1000000
B. 1000000
C. 1000000000
D. > 1000000000
A

D. > 1000000000

47
Q 
Magnetic fields are created by
A. Stationary electric charges
B. moving electric charges 
C. Electric currents
D. B and C
A

D. B and C

48
Q 
A magnetic field strength of .5T is equivalent to
A. 15000G
B. 1500G
C. 5000G
D. 500G
A

C. 5000 G

49
Q

Faraday’s law states that
A. A changing magnetic flux creates an electric field
B. a changing electric flux creates a magnetic field
C. The speed of light is a universal constant
D. A and B

A

D. A and B

50
Q 
In what part of the electromagnetic spectrum does MRI operate
A. Visible
B. x ray
C. Microwave
D. FM
A

D. FM

51
Q

Which factors account for hydrogen being the nucleus of choice for clinical MRI
I. Relative abundance
II. Even number of nucleons
III. Favorable resonance frequency range

A. I and II
B. I and III
C. II ad III
D. I II and III

A

B. I and III

52
Q 
In the rotating reference frame the magnetization M precesses about the rf magnetic field at what rate?
A. ω0=γΒ0
Β. ω1=γΒ1
C. No precession in rotating frame
D. None of the above
A

B. ω1=γΒ1

53
Q 
The pulse sequence interval from the initial 90° rf pulse to the collection of the mr signal is termed
A. TR
B. TE
C. tau
D. B and C
A

B. TE

54
Q 
Suppose that the rf pulse time τrf is some fixed value.  How ,uCi power is required for a 180° FA compared to a 90° FA
A. 1/2
B. 1/4
C. 2
D. 4
A

D. 4

55
Q 
To reduce T2* decay it is best to choose
A. TR short
B. TR long
C. TE short
D. TE long
A

C. TE short

56
Q 
The correct order from smallest frequency to largest frequency is 
A. Radio waves, x rays, visible light
B. radio waves, visible light, x rays
C. X rays, visible light, radio waves
D. None of the above
A

B. radio waves, visible light, x rays

57
Q 
For hydrogen protons in thermal equilibrium in a magnetic field B0
A. # spin up > # spin down
B. #spin up < # spin down
C. # spin up = # spin down
D. Either A or B
A

A. Spin up > spin down

58
Q 
Which members of the following two pairs is larger (1T or 1 G) and (1μs or 1 ms)
A. 1T, 1μs
B. 1T, 1ms
C. 1G , 1μs
D. 1G, 1ms
A

B. 1T, 1ms

59
Q

MRI resonating with electrons at B0 = 1.5T would
A. Require radio waves
B. have a larmor resonance frequency of 64MHz
C. Require microwaves
D. B and C

A

C. Require microwaves

60
Q 
The amount I'd magnetization flipped into the transverse plane will depend on which factors
I. Initial longitudinal magnetization at time of rf pulse
II. TE
III. FA
A. I
B. I and III
C. III
D. I II and III
A

B. I and III

61
Q 
MRI pictures show what basic property
A. X ray attenuation
B. radio wave attenuation
C. Proton density
D. None of the above
A

C. Proton density

62
Q

Longitudinal refers to what direction in MRI
A. Parallel to the static field
B. perpendicular to the static field
C. Either a or b depending on the orientation of the magnetization
D. None of the above

A

A. Parallel to the magnetic field

63
Q 
By MRI convention the static magnetic field is represented by 
A. B0
B. B1
C. M0
D. Mz
A

A. B0

64
Q 
If B = (1+χ)H the Gadolinium has
A. χ=0
Β. χ>0
C. χ<0
D. B or C depending on the diamagnetism
A

Β. χ>0

65
Q 
Α longer TE
A. Increase T1
B. decreases T1
C. Increases T2
D. Decreases T2
A

C. Increases T2

66
Q 
The vector sum of the magnetic moment vectors per unit volume from a voxel of spins is called
A. The B1 magnetic field
B. the B0 magnetic field
C. The net magnetization vector
D. None of the above
A

C. The net magnetization vector

67
Q 
7500ms is how many seconds?
A. 7,500,000
B. 75
C. 7.5
D. .75
A

C. 7.5

68
Q 
After a 90° RF pulse which time is closest for Mz to recover 99% of its equilibrium value
A. T1
B. 2T1
C. 5T1
D. 10T1
A

C. 5T1

69
Q 
For the relaxation times which of the following is true
A. T2*>T2>T1
B. T2>T2*>T1
C. T2*<T2<T1
D. T2<T2*<T1
A

C. T2*<T2<T1

70
Q 
Spin lattice relaxation involves the \_\_\_\_\_ magnetization, while spin son relaxation involves the \_\_\_\_\_ magnetization 
A. Equilibrium, longitudinal
B. longitudinal, equilibrium
C. Transverse, longitudinal
D. Longitudinal, transverse
A

D. Longitudinal, transverse

71
Q 
Which relaxation rate is the greatest
A. R1
B. R2
C. R2*
D. B and C
A

C. R2*

72
Q 
Dephasing is related to which process 
A. Spin lattice relaxation
B. spin spin relaxation
C. Transverse relaxation
D. B and C
A

D. B and C

73
Q

Compared to the gyro magnetic ratio for H protons γp, the gyro magnetic ratio for H electrons γe is
A.γe=γp
B.γe>γp
C.γe<γp
D. B or C depending on the chemical species

A

B. γe>γp

74
Q 
Magnetic susceptibility is related to
A. Electron spin states
B. nuclear spin states
C. A and B
D. None of the above
A

A. Electron spin states

75
Q 
NMR stands for
A. Nuclear moment resistance
B. nuclear magnetic resistance
C. Nuclear magnetic resonance
D. No more relaxation
A

C. Nuclear magnetic resonance

76
Q 
\_\_\_\_\_\_ images tend to have higher SNR and anatomic detail, while \_\_\_\_\_ images are more diagnostic for pathology
A. T1,T1
B. T1,T2
C. T2,T1
D. T2,T2
A

B. T1,T2

77
Q 
Which of the following tissues has the shortest T1 recovery time
A. Edema
B. CSF
C. White matter
D. Gray matter
A

C. White matter

78
Q 
If all other parameters are the same, how much more RF power is required for a dual SE sequence, compared to a GRE sequence with a 45° FA
A. 3
B. 10
C. 36
D. None of the above
A

C. 36

79
Q 
After a 90° RF pulse how much transverse magnetization will remain, compared to the initial value, from some particular species if the TE=T2
A. 33%
B. 37%
C. 63%
D.67%
A

B. 37%

80
Q 
Traditionally the Z direction in MRI is along 
A. The longitudinal direction
B. the direction of the static field
C. B0
D. All of the above
A

D. All of the above

81
Q 
Which of the following have an electric charge
I. Electrons
II. Protons
III. Photons
IV. Neutrons

A. I and II
B. I II and III
C. I II and IV
D. III and IV

A

A. I and II

82
Q 
Concerning the spin lattice interaction, which tissue has natural notional frequencies closest to the larmor frequency of H protons
A. Water
B. solids
C. Fats
D. A and B
A

C. Fats

83
Q 
With similar window and level on which kind of image would CSF be brightest
A. PD
B. T1
C. T2
D. Depends on the exact location of CSF
A

C. T2

84
Q

With similar window and level on which kind of image would fat be the brightest
A. PD
B. T1
C. T2
D. Depends on the exact location of the fat

A

B. T1

85
Q 
Which factors would tend to increase SNR
I. High PD
II. Long TE
III. High B0
IV. GRE instead of SE

A. I
B. I and III
C. I II and IV
D. II and IV

A

B. I and III

86
Q 
For PD weighted images one requires
A. Short TR and TE
B. short TR and long TE
C. Long TR short TE
D. Long TR and TE
A

C. Long TR and Short TE

87
Q 
A dual SE sequence with asymmetric echoes has
A. TE2=2(TE1)
Β. τ2=τ1
C. A and B
D. None of the above
A

D. None of the above

88
Q 
Gradient fields are used to alter the
A. Static field
B. rf field
C. A and B
D. None of the above
A

A. Static field

89
Q 
If the symbols below have their usual meaning, the precession phase φ is best described by which relation?
A. φ= Gx
B. φ= 2τ
C. φ=ωt
D. φ=γΒ
A

C. φ=ωt

90
Q 
What gradient polarity is required to rephase a gradient echo which has been dephased by a negative gradient lobe?
A. 90°
B. 180°
C. Negative
D. Positive
A

D. Positive

91
Q 
The position where the magnetic field is unaffected by the gradients is called
A. Central frequency
B. larmor frequency
C. Isofrequency
D. None of the above
A

D. None of the above

92
Q 
For a CSE choosing a TR of 500 would produce what kind of image
A. T1
B. T 2
C. PD
D. All of the above
A

A. T1

93
Q 
T2W requires
A. Short TR and TE
B. short TR long TE
C. Long TR short TE
D. Long TR and TE
A

D. Long TR and TE

94
Q 
Which of the following substances are ferromagnetic
I. Tin
II. Nickel
III. Manganese
IV. Iron

A. I II IV
B. II, III IV
C. II IV
D. I II III IV

A

C. II IV

95
Q 
Magnetic susceptibility effects are due to 
A. Electrons
B. protons
C. A and B 
D. None of the above
A

C. A and B

96
Q 
Proton density refers to which kind of protons 
A. Mobile
B. bound
C. A and B
D. None of the above
A

A. Mobile

97
Q 
T1W requires
A. Short TR TE
B. Short TR long TE
C. Long TR short TE
D. Long TR TE
A

A. Short TR TE

98
Q 
What kind of magnetic substance is hemosiderin
A. Diamagnetic
B. paramagnetic
C. Superparamagnetic
D. Ferromagnetic
A

C. Super paramagnetic

MRI (6 decks)

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