MRI Physics 1 Flashcards
(99 cards)
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
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%
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
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
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
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
6
Q
By MRI convention the equilibrium magnetization is represented by: A. B0 B. B1 C. M0 D. Mz
A
C. M0
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
8
Q
The rate of decay of an FID is given by A. T1 B. T1* C. T2 D. T2*
A
D. T2*
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
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
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
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
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
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
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
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
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
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
19
Q
What is the time between two successive RF excitation pulses called A. Tau B. TE C. TR D. T1
A
C. TR
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
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
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°
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
24
```
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
```
B. the gyro magnetic ratio
25
```
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
```
B. in the transverse plane
26
```
Magnetic susceptibility effects are seen most prominent in which pulse sequences below
A. IR
B. CSE
C. GRE
D. FSE
```
C. GRE
27
```
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
```
C. Free induction decay
28
```
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
```
C. 2000 ms or greater
29
```
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
```
D. τ= TE/2
30
```
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
```
D. PD 1st T 2 2nd
31
```
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
```
C. 80.9 MHz
32
```
Which pulse sequence usually converts only a portion of the longitudinal magnetization into transverse magnetization?
A. IR
B. SE
C. FSE
D. GRE
```
D. GRE
33
```
A typical time duration for an RF pulse might be?
A. 500ms
B. 500μs
C. .5ms
D. B and C
```
D. B and C
34
```
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
```
B. T1 increases
35
```
In relation to the static magnetic field the B1 magnetic field is oriented
A. Parallel
B. perpendicular
C. At 180°
D. At 45°
```
B. perpendicular
36
```
What is the decay rate for an FID?
A. R1
B. R2
C. R2*
D. None of the above
```
C. R2*
37
```
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
```
C. Excitation
38
```
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
```
D. A and B
39
```
Which of the following tissues has the longest T 2 decay time?
A. CSF
B. white matter
C. Gray matter
D. Fat
```
A. CSF
40
Put the following wavelengths in order from smallest to largest
X-rays radio waves and microwaves
Radiowaves, microwaves, x-rays
41
```
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
```
C. 4
42
```
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
```
D. Fat T1< water T1 Water T2> Fat T2
43
```
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. Number of protons
44
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
B. I and II
45
```
On a dual echo SE pulse sequence for the brain with long TR and TE1
B. T2
46
```
About how many hydrogen proton spins are there in a 1mm^3 vowel of fat
A. < 1000000
B. 1000000
C. 1000000000
D. > 1000000000
```
D. > 1000000000
47
```
Magnetic fields are created by
A. Stationary electric charges
B. moving electric charges
C. Electric currents
D. B and C
```
D. B and C
48
```
A magnetic field strength of .5T is equivalent to
A. 15000G
B. 1500G
C. 5000G
D. 500G
```
C. 5000 G
49
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
D. A and B
50
```
In what part of the electromagnetic spectrum does MRI operate
A. Visible
B. x ray
C. Microwave
D. FM
```
D. FM
51
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
B. I and III
52
```
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
```
B. ω1=γΒ1
53
```
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
```
B. TE
54
```
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
```
D. 4
55
```
To reduce T2* decay it is best to choose
A. TR short
B. TR long
C. TE short
D. TE long
```
C. TE short
56
```
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
```
B. radio waves, visible light, x rays
57
```
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. Spin up > spin down
58
```
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
```
B. 1T, 1ms
59
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
C. Require microwaves
60
```
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
```
B. I and III
61
```
MRI pictures show what basic property
A. X ray attenuation
B. radio wave attenuation
C. Proton density
D. None of the above
```
C. Proton density
62
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. Parallel to the magnetic field
63
```
By MRI convention the static magnetic field is represented by
A. B0
B. B1
C. M0
D. Mz
```
A. B0
64
```
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
```
Β. χ>0
65
```
Α longer TE
A. Increase T1
B. decreases T1
C. Increases T2
D. Decreases T2
```
C. Increases T2
66
```
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
```
C. The net magnetization vector
67
```
7500ms is how many seconds?
A. 7,500,000
B. 75
C. 7.5
D. .75
```
C. 7.5
68
```
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
```
C. 5T1
69
```
For the relaxation times which of the following is true
A. T2*>T2>T1
B. T2>T2*>T1
C. T2*
C. T2*
70
```
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
```
D. Longitudinal, transverse
71
```
Which relaxation rate is the greatest
A. R1
B. R2
C. R2*
D. B and C
```
C. R2*
72
```
Dephasing is related to which process
A. Spin lattice relaxation
B. spin spin relaxation
C. Transverse relaxation
D. B and C
```
D. B and C
73
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
B. γe>γp
74
```
Magnetic susceptibility is related to
A. Electron spin states
B. nuclear spin states
C. A and B
D. None of the above
```
A. Electron spin states
75
```
NMR stands for
A. Nuclear moment resistance
B. nuclear magnetic resistance
C. Nuclear magnetic resonance
D. No more relaxation
```
C. Nuclear magnetic resonance
76
```
______ 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
```
B. T1,T2
77
```
Which of the following tissues has the shortest T1 recovery time
A. Edema
B. CSF
C. White matter
D. Gray matter
```
C. White matter
78
```
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
```
C. 36
79
```
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%
```
B. 37%
80
```
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
```
D. All of the above
81
```
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. I and II
82
```
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
```
C. Fats
83
```
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
```
C. T2
84
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
B. T1
85
```
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
B. I and III
86
```
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
```
C. Long TR and Short TE
87
```
A dual SE sequence with asymmetric echoes has
A. TE2=2(TE1)
Β. τ2=τ1
C. A and B
D. None of the above
```
D. None of the above
88
```
Gradient fields are used to alter the
A. Static field
B. rf field
C. A and B
D. None of the above
```
A. Static field
89
```
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
```
C. φ=ωt
90
```
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
```
D. Positive
91
```
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
```
D. None of the above
92
```
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. T1
93
```
T2W requires
A. Short TR and TE
B. short TR long TE
C. Long TR short TE
D. Long TR and TE
```
D. Long TR and TE
94
```
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
C. II IV
95
```
Magnetic susceptibility effects are due to
A. Electrons
B. protons
C. A and B
D. None of the above
```
C. A and B
96
```
Proton density refers to which kind of protons
A. Mobile
B. bound
C. A and B
D. None of the above
```
A. Mobile
97
```
T1W requires
A. Short TR TE
B. Short TR long TE
C. Long TR short TE
D. Long TR TE
```
A. Short TR TE
98
```
What kind of magnetic substance is hemosiderin
A. Diamagnetic
B. paramagnetic
C. Superparamagnetic
D. Ferromagnetic
```
C. Super paramagnetic
-
Key Links
-
Subjects
-
Company
-
Find Us
-
