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MRI in practice 5th ed. > Chapter 1 > Flashcards

Chapter 1 Flashcards

Basic Principles

1
Q

With a precessional frequency of 63 MHz, what is the approximate field strength of the magnet?

a. 2.0 Tesla
b. 1.5 Tesla
c. 0.5 Tesla
d. 0.3 Tesla

A

b. 1.5 Tesla

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2
Q

If the magnetic field to which the patient is exposed is decreased, what happens to the precessional frequency?

a. it decreases
b. it increases
c. it does not change
d. it would stop

A

a. it decreases

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3
Q

Which of the following is true of moving charged particles?

a. they generate x-rays
b. they generate a gravitational field
c. they generate a magnetic field
d. none of these

A

c. they generate a magnetic field

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4
Q

Which of the following is not a requirement for magnetic resonance imaging?

a. a strong magnetic field
b. atomic nuclei with an odd number of protons
c. ionizing radiation
d. RF energy

A

c. ionizing radiation

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5
Q

The precessional frequency of protons in a magnetic field is determined by:

a. the gyromagnetic ratio
b. the magnetic field strength
c. both a & b
d. none of these

A

c. both a & b

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6
Q

Which of the following is true of protons aligned parallel with the magnetic field of the MR system compared to those aligned against it?

a. there are more of them
b. they are in a higher energy state
c. neither of these
d. both of these

A

a. there are more of them

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7
Q

In a pulse sequence, the time from the excitation pulse to the echo is called the:

a. TI
b. TE
c. TR
d. TD

A

b. TE

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8
Q

The time from the initial RF excitation pulse to the next excitation pulse is known as…

a. TI
b. TR
c. TE
d. T2

A

b. TR

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9
Q

The degree to which the NMV moves out of alignment with the main magnetic field is referred to as…

a. Flip Angle
b. Resonance
c. Regrowth
d. Relaxation

A

a. Flip Angle

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10
Q

When the RF Pulse is removed…

a. resonance occurs
b. protons begin to spin in phase
c. protons begin to spin out of phase
d. the main magnetic field loses strength

A

c. protons begin to spin out of phase

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11
Q

The gyro-magnetic ratio of hydrogen at 1 Tesla is…

a. 63.86
b. 42.57
c. 21.28
d. 127.71

A

b. 42.57

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12
Q

Following the removal of the RF pulse as the protons return to equilibrium the signal given is called…

a. T1 signal
b. T2 signal
c. in phase signal
d. (FID) free induction decay signal

A

d. (FID) free induction decay signal

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13
Q

A vector is a quantity that…

a. represents precession
b. has both magnitude and direction
c. demonstrates Faraday’s Law
d. proves the Larmor equation

A

b. has both magnitude and direction

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14
Q

Before the patient enters the main magnetic field, the atoms…

a. precess
b. are in equilibrium
c. are in phase
d. are in random alignment

A

d. are in random alignment

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15
Q

A signal is only induced in the receiver coil if there is _______ in the transverse plane.

a. coherent magnetization
b. incoherent magnetization
c. corporeal magnetization
d. disembodied magnetization

A

a. coherent magnetization

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16
Q

The isotope of the hydrogen nucleus called _______ is the MR active nucleus used in clinical MRI.

a. platinum
b. palladium
c. promethium
d. protium

A

d. protium

17
Q

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

a. resonance
b. the Larmor effect
c. excitation
d. phasing

A

c. excitation

18
Q

The process of relaxation begins when:

a. B0 is turned off
b. B1 is turned off
c. B1 is turned on
d. B0 is turned on

A

b. B1 is turned off

19
Q

Magnetic Resonance Imaging is derived from the process known as:

a. Magnetic resonance angiography
b. Magnetic relaxation imaging
c. Nuclear magnetic resonance
d. Nuclear resonance imaging

A

c. Nuclear magnetic resonance

20
Q

One Tesla is the equivalent of:

a. 10 gauss
b. 1000 gauss
c. 10,000 gauss
d. 100,000 gauss

A

c. 10,000 gauss

21
Q

In the main magnetic field, protons that are oriented parallel and those that are oriented anti-parallel will have what effect on each other?

a. Add to their magnetic moments
b. Subtract from their magnetic moments
c. Have no effect
d. Cancel their magnetic moments

A

d. Cancel their magnetic moments

22
Q

In MRI, substances respond to a specific radio frequency which is known as the:

a. Larmor frequency
b. Radio frequency
c. Magnetic frequency
d. Gyro-magnetic frequency

A

a. Larmor frequency

23
Q

At any one time, human body tissue is made up of 50% - 90% of what substance?

a. C13
b. NA 23
c. H2O
d. Gd

A

c. H2O

24
Q

On a very basic level, the three main components required to attain MR signals are:

a. Magnetic field, proton, ionizing radiation
b. Magnetic field, electron, ionizing radiation
c. Magnetic field, electron, radio-wave
d. Magnetic field, proton, radio-wave

A

d. Magnetic field, proton, radio-wave

25
Q

In MRI, for a chemical substance to be affected by the main magnetic field and the radio wave it must contain an:

a. Odd number of electrons
b. Odd number of total protons and neutrons
c. Even number of total electrons and neutrons
d. Even number of protons

A

b. Odd number of total protons and neutrons

26
Q

A 90 degree RF pulse will alter the NMV. Another effect is:

a. The hydrogen protons will precess randomly
b. The hydrogen protons will have phase coherence
c. The hydrogen protons will dephase
d. The hydrogen protons will rephase

A

b. The hydrogen protons will have phase coherence

27
Q

Which of the following is the Larmor equation?

a. B0 = λ + ω0
b. B0 = λ x ω0
c. λ = B0 – ω0
d. ω0 = λ x B0

A

d. ω0 = λ x B0

28
Q

The basic process of MR signal generation contains two steps:

a. Parallel alignment and anti-parallel alignment
b. Magnetization and ionization
c. Excitation and relaxation
d. Spatial localization and Fourier transform

A

c. Excitation and relaxation

29
Q

During thermal equilibrium there are:

a. More spins in the low energy state
b. More spins in the high energy state
c. Equal number of spins in the low and high energy state
d. Less spins in the low energy state

A

a. More spins in the low energy state

30
Q

In the Larmor equation, B0 stands for:

a. Static magnetic field
b. Frequency
c. Gyromagnetic ratio
d. Voltage

A

a. Static magnetic field

31
Q

In the Larmor equation, λ stands for:

a. Static magnetic field
b. Frequency
c. Gyromagnetic ratio
d. Voltage

A

c. Gyromagnetic ratio

32
Q

In the Larmor equation, ω0 stands for:

a. Static magnetic field
b. Frequency
c. Gyromagnetic ratio
d. Voltage

A

b. Frequency

33
Q

A _________ radiofrequency pulse converts all longitudinal magnetization to transverse magnetization.

a. less than 90 degree
b. greater than 90 degree
c. 90 degree
d. 180 degree

A

c. 90 degree

34
Q

Although at equilibrium the magnetization only points along the axis of the main magnetic field, in general it can point in any direction. The magnetization is a vector quantity that can be represented by a “longitudinal” component along the ______.

a. z-axis
b. x-axis
c. y-axis
d. xy-plane

A

a. z-axis

35
Q

With a precessional frequency of 21.2 MHz, what is the approximate field strength of the magnet?
a. 2.0 Tesla
b 1.5 Tesla
c. 0.5 Tesla
d. 0.3 Tesla

A

c. 0.5 Tesla

36
Q

If the magnetic field to which the patient is exposed is increased, what happens to the precessional frequency?

a. it decreases
b. it increases
c. it does not change
d. it would stop

A

b. it increases

37
Q

There are essentially two ways of explaining the fundamentals of MRI:

a. Vacuum theory and via quantum mechanics
b. Classically and via quantum mechanics
c. Velocity and acceleration theory
d. Classically and via quality mechanics

A

b. Classically and via quantum mechanics

38
Q

Frequency of a RF pulse should be approximately _____MHz in order to excite protons in a 3 Tesla magnet

a. 64
b. 128
c. 170
d. 42.57

A

b. 128

MRI in practice 5th ed. (10 decks)

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