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MRI Physics > week 1 final > Flashcards

week 1 final Flashcards

1
Q

Calculate the scan time for a fast spin echo sequence with the following parameters: TR 500, TE 24, FOV 20cm 224 x 256 matrix, 4 NEX, 5 ETL, 4 mm slice thickness.

A

1 min. 29 sec.

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2
Q

The hydrogen proton induces a strong magnetic field because it is:

A

Charged and spinning

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3
Q

The more ETL, the more _____________ is needed.

A

TR

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4
Q

Energy is most effectively transferred from one system to another when the systems are at:

A

Resonance

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5
Q

Which of the following is always on?

A

B0

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6
Q

Relaxation Time refers to:

A

Time required for the nuclear spin to return to equilibrium

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7
Q

T1 weighted images are characterized by:

A

Bright fat and dark water

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8
Q

What level of sedation requires physiological monitoring?

A

All of the above (Parenteral, Enteral, General Anesthesia, Any patient unconscious)

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9
Q

Who is responsible for monitoring a patient who is connected to physiological vital signs equipment?

A

Advanced level care personnel such as RN

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10
Q

The purpose of a chelating agent such as DTPA is:

A

Neutralize the toxicity of a metal ion

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11
Q

What happens to the hydrogen protons when they are placed in a magnetic field?

A

They align parallel or anti-parallel

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12
Q

Calculate the scan time for a 3D gradient echo sequence with the following parameters: FOV 16, TR 25, TE 12, 208 x 256 matrix, 1 NEX, 4mm slice thickness, 36 slices.

A

3 min. 7 sec.

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13
Q

In MR imaging, the term “spin” refers specifically to the spinning:

A

Nuclei

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14
Q

The tiny magnetic field of the hydrogen proton that is induced by spin and charge and has a north and south pole is called:

A

Magnetic moment

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15
Q

Calculate the scan time for a fast spin echo sequence with the following parameters: TR 3000, TE 100, 512 x 512 matrix, 2 NEX, 5 mm slice thickness, 18 ETL.

A

2 min. 50 sec.

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16
Q

What is the FDA recommended amount of SAR for whole body averaged over 15 minutes?

A

4 W/kg

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17
Q

What is the most important safety consideration associated with a quench?

A

Displacement of oxygen

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18
Q

The Larmor precessional frequency of hydrogen in a 3T magnet is:

A

127.74 MHz

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19
Q

What extrinsic factor controls the amount of T2 decay?

A

TE

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20
Q

What is “DRIVE”?

A

A reverse 90-degree pulse

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21
Q

Calculate the scan time for a 3D gradient echo sequence with the following parameters: FOV 16, TR 20, TE 9, 192 x 256 matrix, 2 NEX, 5mm slice thickness, 40 slices.

A

5 min. 7sec.

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22
Q

What weighted image would be created with the following parameters: TR 15, TE 2, FA 25?

A

T2*

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23
Q

GRE T2*-weighted sequences use:

A

Gradient or RF spoiling

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24
Q

Dynamic enhanced T1 weighted MRA sequences of the renal arteries are performed with the use of:

A

Incoherent gradient echoes

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25
Q

The nucleus of a hydrogen atom contains:

A

One proton

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26
Q

The symbol for the primary static field is:

A

Bₒ

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27
Q

What is the 5 Gauss line?

A

The magnetic field strength and distance that is safe for a person with any device

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28
Q

T1 and T2 relaxation depends on:

A

Molecular tumbling rate matching Larmor frequency of hydrogen

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29
Q

What physiological monitoring device should be employed when a patient is heavily sedated for an MR exam?

A

All of the above (Pulse oximetry, Blood pressure, ECG)

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30
Q

What is NSF?

A

Nephrogenic systemic fibrosis

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31
Q

What is the primary purpose of gradient coils in MRI?

A

Spatial localization of the MRI signal

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32
Q

What is the main function of the RF coil in MRI?

A

Transmitting and receiving RF pulses

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33
Q

What determines the Larmor frequency of hydrogen?

A

Strength of the external magnetic field

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34
Q

What is the most important safety concern associated with MRI?

A

Ferromagnetic attraction

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35
Q

Who can sign the MRI screening form?

A

A, B, and C (Patient of legal age, legal representative, legal guardian)

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36
Q

What weighted image would be created with the following parameters: TR 500, TE 10, FA 90?

A

T1

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37
Q

What tissue is bright on diffusion-weighted imaging?

A

Abnormal tissue and tissue with low ADC

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38
Q

The time constant of the precessional frequency of a specific MR-active nucleus at 1 Tesla in MHz/T is called:

A

Gyromagnetic ratio

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39
Q

What determines the amount of ferromagnetic reaction/attraction?

A

All of the above (Size, shape, and material composition)

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40
Q

Whose law states that ‘a moving electric current creates a magnetic field’?

A

Michael Faraday

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41
Q

What is the Tesla strength for the Larmor precessional frequency of 170.32 MHz?

A

4T

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42
Q

What is a pulse oximeter?

A

A device that measures blood oxygen levels

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43
Q

SE scan time formula is:

A

TR × Phase matrix × NSA

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44
Q

The point in a tissue’s longitudinal recovery where no magnetization remains and no signal is created on an IR pulse sequence is called:

A

Null point

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45
Q

T2-weighted, fluid-attenuated inversion recovery (FLAIR) sequences are typically used for the evaluation of:

A

Periventricular white matter disease such as multiple sclerosis

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46
Q

Which combination of TE and TR creates a PD-weighted image?

A

Short TE, long TR

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47
Q

Gradient echo sequences acquired for high signal from fluid are known as all of the following EXCEPT:

A

Incoherent gradient echoes

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48
Q

Calculate the scan time for a fast spin echo with the following parameters: FOV 20cm, TR 3000, TE 120, 224 × 256 matrix, 3 NEX, 5 mm slice thickness, 12 ETL.

A

2 min. 48 sec.

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49
Q

What can cause NSF?

A

Certain types of gadolinium contrast remaining in the human body too long

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50
Q

Phase is:

A

A position at a given time

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51
Q

What were the early NMR machines used to study, and what was the name of this technique?

A

Chemicals, spectroscopy

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52
Q

A person who is allergic to seafood will have an allergic reaction to IV gadolinium contrast.

A

False

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53
Q

What zone should screening be completed in?

A

Zone 3

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54
Q

The application of an RF pulse that causes resonance to occur is termed:

A

Excitation

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55
Q

One of the reasons that the hydrogen atom is used in clinical MR imaging is its abundance in the body and:

A

Its solitary proton creates a large magnetic moment

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56
Q

What is a typical TI time for T2 FLAIR?

A

1700-2200 ms

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57
Q

What is a ‘quench’?

A

Sudden loss of liquid helium and magnetic field

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58
Q

In a dual-echo sequence for proton density and T2 weighting, which echo is the proton density?

A

TE 20ms

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59
Q

What is the term used to describe the rapid loss of superconductivity in an MRI magnet, resulting in the release of helium gas?

A

Quench

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60
Q

A condition where the TR is less than T1 and T2 relaxation times of tissues, where energy in equals energy out, is known as:

A

Steady state

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61
Q

What is the Ernst angle?

A

Flip angle that provides optimum signal intensity

62
Q

What weighted image would be created with FSE, TR 6000, TE 100, ETL 16?

A

T2

63
Q

Who was the first person to demonstrate a radio signal from the nucleus of an atom?

A

Isidor Rabi

64
Q

Which of the following best describes an EPI sequence?

A

A “train” of gradient echoes

65
Q

Gradient echo T1-weighted sequences use:

A

Gradient or RF spoiling

66
Q

What is the most important safety consideration for a patient who has had a cardiac pacemaker removed?

A

That the pacer wires are still in the patient’s body

67
Q

What is the first thing that should be done for a patient who is having a medical emergency during an MRI?

A

Remove the patient from the scanner, place them in zone 3, secure the MRI scan room door, and then call for help

68
Q

TR 9000, TE 125, TI 2200, FM 256, PM 224, 10 ETL, slice thickness 5mm, 2mm gap would yield images with what weighting?

A

T2 FLAIR

69
Q

What is the temperature of liquid helium?

A

4 K / -270 degrees C / -452 degrees F

70
Q

What is the FDA-recommended amount of SAR for the head averaged over 10 minutes?

A

3 W/kg

71
Q

In STIR sequences, which tissue is being suppressed?

A

Fat

72
Q

What is a cochlear implant?

A

An implant in the inner ear

73
Q

What conditions are necessary for resonance?

A

Energy applied at the precise frequency and at a right angle

74
Q

An advantage of using gradient echo sequences is:

A

Faster scan times

75
Q

Calculate the scan time for a fast spin echo sequence with the following parameters: FOV 16cm, TR 2500, TE 90, 224 x 256 matrix, 6 NEX, 5mm slice thickness, 18 ETL.

A

3.11 minutes

76
Q

Calculate the scan time for a fast spin echo with the following parameters: TR 3500, TE 100, 256 x 256 matrix, 4 NEX, 5mm slice thickness, 14 ETL.

A

4 min. 16 sec.

77
Q

Which statement is NOT true about FSE T2 pulse sequences?

A

Fat is darker than on SE pulse sequences

78
Q

GRE with a small flip angle, long TR, short TE would yield:

A

PD weighted

79
Q

In IR sequences, the resultant contrast depends primarily on the:

A

TI

80
Q

All patients with joint replacements can safely undergo an MRI.

A

False

81
Q

A patient with a spinal cord stimulator can never be scanned with MRI.

A

False

82
Q

Spin echo sequences are useful for:

A

A, B, and C only (T1, T2, and PD weighted images)

83
Q

Precessional frequency in MRI is measured in:

A

MHz

84
Q

FSE/TSE sequences are useful for:

A

A, B, and C only (T1, T2, and PD weighted images)

85
Q

Where can you find the latest information regarding MRI registry?

A

ARRT.org

86
Q

A TI time of 150ms on a 1.5T magnet will null the signal from what tissue?

A

Fat

87
Q

Arthrographic means:

A

Visualize joint spaces

88
Q

What does GRASE stand for?

A

Gradient echo and spin echo

89
Q

Which of the following is NOT one of the intrinsic contrast parameters?

A

TR

90
Q

What is a transdermal patch?

A

A medication delivery device

91
Q

When would a tattoo be considered MR unsafe?

A

If it has iron oxide inks

92
Q

Myelographic means:

A

Spinal cord and nerve visualization

93
Q

Calculate the scan time for a spin echo sequence with the following parameters: TR 500, TE 25, 224 x 256 matrix, 2 NSA, 3mm slice thickness.

A

3 min 44 sec

94
Q

What is required if the MRI table is not detachable?

A

There must be an MRI-safe gurney readily available

95
Q

Gradient echo sequences acquired for the evaluation of hemorrhagic lesions rely on:

A

Susceptibility

96
Q

What is the precessional frequency for hydrogen on a 5T external static magnetic field?

A

212.9 MHz

97
Q

What type of echoes are generated in EPI?

A

Gradient echoes

98
Q

What extrinsic factor controls the amount of T1 recovery?

A

TR

99
Q

If a quench has occurred, the operator should evacuate the room to avoid:

A

Asphyxiation and frostbite

100
Q

Calculate the scan time for a 3D GRE echo sequence with the following parameters: TR 40, TE 24; FOV 30; 192 x 256 matrix; 1 NSA, F/A 45; 3.5 mm slice thickness; 31 slices.

A

3 min. 58 sec.

101
Q

Imaging parameters in GRE T1-weighted sequences should have:

A

Large flip angle, short TR, short TE

102
Q

What is the extrinsic contrast parameter unique to TSE/FSE?

A

Turbo factor or echo train length

103
Q

What signal/s are sampled in coherent or rewind GE sequences?

A

The FID and the stimulated echo

104
Q

What is the scan time for a proton density-weighted image assuming the following parameters: TR 3000ms, TE 20; 256 x 256, NSA 1, ETL 4?

A

3 minutes 12 seconds

105
Q

The pulse sequence consisting of a variable flip angle RF excitation pulse followed by a pulse of the magnetic field gradients is called:

A

Gradient echo

106
Q

What weighted image would be created with a CSE, TR 600, and TE 15?

A

T1

107
Q

Where is a common place for a vascular filter?

A

IVC

108
Q

Imaging parameters in GRE T2*-weighted sequences should have:

A

Small flip angle, long TR, long TE

109
Q

A gradient echo sequence in which any residual transverse magnetization is removed prior to the next excitation pulse is known as:

A

Incoherent/spoiled

110
Q

With regard to energy, protons in parallel alignment are in the _________ state, whereas protons in anti-parallel alignment are in the __________ state.

A

Low, high

111
Q

STIR sequences can suppress the signal from all of the following EXCEPT:

A

Fluid (CSF)

112
Q

The B1 magnetic field is produced by:

A

RF coil

113
Q

The null point of a tissue in an IR pulse sequence is calculated by:

A

0.69 x the T1 relaxation time of a tissue

114
Q

The following parameters are suitable in a T2 FLAIR sequence EXCEPT:

A

Short TE to enhance T2 weighting

115
Q

What image would be created with the following parameters: TR 2000, TE 60, TI 150?

A

STIR

116
Q

What zone should all persons be supervised?

A

Zones 3 and 4

117
Q

Spins aligned in the anti-parallel direction are in __________.

A

A high energy state

118
Q

What is the Larmor equation used to calculate?

A

Precessional frequency

119
Q

A technique that uses the differences in magnetic susceptibility between oxyhemoglobin and deoxyhemoglobin to image areas of activated cerebral cortex is:

A

BOLD

120
Q

A rapid acquisition technique that begins with a sequence of one or more RF pulses and is followed by a series of gradient echoes:

A

EPI

121
Q

What is an ‘active’ implant?

A

An implanted device that has a power source other than the human body itself

122
Q

Which of the following is not one of the extrinsic parameters?

A

Proton Density (PD)

123
Q

Angiographic means:

A

Visualize blood vessels and flow

124
Q

What is a Hahn echo?

A

Any two 90° RF pulses produce one

125
Q

In what year did MRI receive its FDA approval?

A

1985

126
Q

Short tau inversion recovery (STIR) images are:

A

T2-weighted, fat-nulled images

127
Q

Who is responsible for verifying that all the custodial staff are educated and trained about MR safety?

A

All MR technologists on staff

128
Q

Which combination of TR and TE create a T1-weighted image?

A

TE 30ms, TR 300ms

129
Q

Why should a patient have their kidney function tested before an MRI is performed with IV gadolinium contrast injection?

A

To make sure the contrast will be filtered out from the body in a reasonable amount of time

130
Q

What type of echoes are generated in EPI?

A

Gradient echoes

131
Q

What extrinsic factor controls the amount of T1 recovery?

A

TR

132
Q

If a quench has occurred, the operator should evacuate the room to avoid:

A

Asphyxiation and frostbite

133
Q

Calculate the scan time for a 3D GRE echo sequence with the following parameters: TR 40, TE 24; FOV 30; 192 x 256 matrix; 1 NSA, FA 45; 3.5 mm slice thickness; 31 slices.

A

3 min. 58 sec.

134
Q

Imaging parameters in GRE T1-weighted sequences should have:

A

Large flip angle, short TR, short TE

135
Q

What is the extrinsic contrast parameter unique to TSE/FSE?

A

Turbo factor or echo train length

136
Q

What signals are sampled in coherent or rewind GE sequences?

A

The FID and the stimulated echo

137
Q

What is the scan time for a proton density weighted image assuming the following parameters: TR 3000ms, TE 20; 256 x 256, NSA 1, ETL 4?

A

3 minutes 12 seconds

138
Q

The pulse sequence consisting of a variable flip angle RF excitation pulse followed by a pulse of the magnetic field gradients is called:

A

Gradient echo

139
Q

What weighted image would be created with a CSE, TR 600, and TE 15?

A

T1

140
Q

Where is a common place for a vascular filter?

A

IVC

141
Q

Imaging parameters in GRE T2*-weighted sequences should have:

A

Small flip angle, long TR, long TE

142
Q

A gradient echo sequence in which any residual transverse magnetization is removed prior to the next excitation pulse is known as:

A

Incoherent/spoiled

143
Q

With regard to energy, protons in parallel alignment are in the _________ state, whereas protons in anti-parallel alignment are in the __________ state.

A

Low, high

144
Q

What is the purpose of the initial RF pulse in a coherent gradient echo sequence?

A

Spin excitation

145
Q

All surgical staples, clips, and metallic sutures are MR unsafe.

A

False

146
Q

T2 relaxation time is defined as when:

A

63% of the transverse magnetization has decayed

147
Q

What is the FDA recommended amount of SAR for the head averaged over 10 minutes?

A

3 W/kg

148
Q

In STIR sequences, which tissue is being suppressed?

A

Fat

149
Q

What is a cochlear implant?

A

An implant in the inner ear

150
Q

What conditions are necessary for resonance?

A

Energy applied at the precise frequency and at a right angle

MRI Physics (6 decks)

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