ARMRIT MRI Technologist
Certification Exam: 100 Practice
Questions and Answer Explanations
Part One: MRI Physics Fundamentals
(1–25)
1. Which subatomic particle is primarily responsible for the magnetic properties of an
atom utilized in MRI?
A. Electron
B. Neutron
C. Proton
D. Photon
Answer: C
Explanation: The hydrogen proton (¹H) is the nucleus used in MRI due to its abundance in
the human body and its magnetic moment. The proton acts like a tiny bar magnet, aligning
with the external magnetic field .
2. In the absence of an external magnetic field, how are nuclear spins oriented?
A. Parallel to the earth's magnetic field
B. Antiparallel to the earth's magnetic field
C. Randomly oriented
D. Aligned with the radiofrequency field
Answer: C
Explanation: In their natural environment without an applied external magnetic field,
nuclear spins have random orientations. When a strong external magnetic field (B₀) is
applied, these spins align either parallel or antiparallel to the field .
3. When a patient is placed inside the MRI scanner's main magnetic field, what happens to
the majority of hydrogen protons?
A. They align antiparallel to B₀
B. They align parallel to B₀
C. They remain randomly oriented
D. They align perpendicular to B₀
Answer: B
Explanation: A slight majority (slightly more than half) align parallel (spin-up) to B₀ because
,this is the lower energy state. The small excess of parallel-aligned protons creates the net
magnetization vector that generates the MR signal .
4. What is precession in the context of MRI?
A. The linear movement of protons through tissue
B. The wobbling motion of nuclear spins around the direction of B₀
C. The emission of gamma rays from excited nuclei
D. The alignment of protons with the RF field
Answer: B
Explanation: Precession is the wobbling or rotating motion of nuclear magnetic moments
around the axis of the main magnetic field (B₀). This motion is analogous to a spinning top
wobbling around the earth's gravitational field .
5. The Larmor equation describes the relationship between which of the following?
A. Tissue density and signal intensity
B. Magnetic field strength and precessional frequency
C. RF pulse duration and flip angle
D. Gradient strength and slice thickness
Answer: B
Explanation: The Larmor equation (ω₀ = γ × B₀) states that the precessional frequency is
directly proportional to the strength of the main magnetic field, with the gyromagnetic ratio
(γ) as the constant of proportionality .
6. What is the gyromagnetic ratio of hydrogen (¹H)?
A. 4.26 MHz/T
B. 42.58 MHz/T
C. 63.87 MHz/T
D. 127.0 MHz/T
Answer: B
Explanation: The gyromagnetic ratio (γ) for hydrogen is approximately 42.58 MHz/T. This
constant determines that at 1.5 Tesla, the Larmor frequency of hydrogen is approximately
63.87 MHz .
7. At 1.5 Tesla, what is the Larmor frequency of hydrogen?
A. 21.3 MHz
B. 42.6 MHz
C. 63.9 MHz
D. 127.8 MHz
Answer: C
Explanation: At 1.5 Tesla: ω = 42.58 MHz/T × 1.5 T = 63.87 MHz .
8. At 3.0 Tesla, what is the Larmor frequency of hydrogen?
A. 21.3 MHz
, B. 42.6 MHz
C. 63.9 MHz
D. 127.7 MHz
Answer: D
Explanation: At 3.0 Tesla: ω = 42.58 MHz/T × 3.0 T = 127.74 MHz .
9. An RF pulse transmitted with a strength and duration sufficient to flip the net
magnetization vector from the Z axis to the XY plane is a(n):
A. 90-degree pulse
B. 180-degree pulse
C. Inversion pulse
D. Gradient pulse
Answer: A
Explanation: A 90° RF pulse tips the net magnetization from the longitudinal to the
transverse plane, where it precesses and induces a detectable signal in the receiver coil .
10. An MR signal is generated when the net magnetization vector is:
A. Along the Z axis
B. At equilibrium
C. Some value greater than zero in the XY plane
D. Completely dephased
Answer: C
Explanation: The MR signal is induced when there is transverse magnetization (Mxy)
precessing in the XY plane. When Mxy is zero, no signal is generated .
11. Following the excitation pulse, the FID decays:
A. Linearly
B. Exponentially
C. During the 180-degree RF pulse
D. Along the Z axis
Answer: B
Explanation: The free induction decay (FID) signal decays exponentially due to T2*
dephasing as the transverse magnetization loses phase coherence .
12. The MR signal is strongest when the precessing nuclei are:
A. In phase coherence
B. Out of phase
C. Aligned with B₀
D. At equilibrium
Answer: A
Explanation: When precessing nuclei are in phase coherence, their individual signals add
together to produce a strong net signal. Dephasing causes signal loss .
Certification Exam: 100 Practice
Questions and Answer Explanations
Part One: MRI Physics Fundamentals
(1–25)
1. Which subatomic particle is primarily responsible for the magnetic properties of an
atom utilized in MRI?
A. Electron
B. Neutron
C. Proton
D. Photon
Answer: C
Explanation: The hydrogen proton (¹H) is the nucleus used in MRI due to its abundance in
the human body and its magnetic moment. The proton acts like a tiny bar magnet, aligning
with the external magnetic field .
2. In the absence of an external magnetic field, how are nuclear spins oriented?
A. Parallel to the earth's magnetic field
B. Antiparallel to the earth's magnetic field
C. Randomly oriented
D. Aligned with the radiofrequency field
Answer: C
Explanation: In their natural environment without an applied external magnetic field,
nuclear spins have random orientations. When a strong external magnetic field (B₀) is
applied, these spins align either parallel or antiparallel to the field .
3. When a patient is placed inside the MRI scanner's main magnetic field, what happens to
the majority of hydrogen protons?
A. They align antiparallel to B₀
B. They align parallel to B₀
C. They remain randomly oriented
D. They align perpendicular to B₀
Answer: B
Explanation: A slight majority (slightly more than half) align parallel (spin-up) to B₀ because
,this is the lower energy state. The small excess of parallel-aligned protons creates the net
magnetization vector that generates the MR signal .
4. What is precession in the context of MRI?
A. The linear movement of protons through tissue
B. The wobbling motion of nuclear spins around the direction of B₀
C. The emission of gamma rays from excited nuclei
D. The alignment of protons with the RF field
Answer: B
Explanation: Precession is the wobbling or rotating motion of nuclear magnetic moments
around the axis of the main magnetic field (B₀). This motion is analogous to a spinning top
wobbling around the earth's gravitational field .
5. The Larmor equation describes the relationship between which of the following?
A. Tissue density and signal intensity
B. Magnetic field strength and precessional frequency
C. RF pulse duration and flip angle
D. Gradient strength and slice thickness
Answer: B
Explanation: The Larmor equation (ω₀ = γ × B₀) states that the precessional frequency is
directly proportional to the strength of the main magnetic field, with the gyromagnetic ratio
(γ) as the constant of proportionality .
6. What is the gyromagnetic ratio of hydrogen (¹H)?
A. 4.26 MHz/T
B. 42.58 MHz/T
C. 63.87 MHz/T
D. 127.0 MHz/T
Answer: B
Explanation: The gyromagnetic ratio (γ) for hydrogen is approximately 42.58 MHz/T. This
constant determines that at 1.5 Tesla, the Larmor frequency of hydrogen is approximately
63.87 MHz .
7. At 1.5 Tesla, what is the Larmor frequency of hydrogen?
A. 21.3 MHz
B. 42.6 MHz
C. 63.9 MHz
D. 127.8 MHz
Answer: C
Explanation: At 1.5 Tesla: ω = 42.58 MHz/T × 1.5 T = 63.87 MHz .
8. At 3.0 Tesla, what is the Larmor frequency of hydrogen?
A. 21.3 MHz
, B. 42.6 MHz
C. 63.9 MHz
D. 127.7 MHz
Answer: D
Explanation: At 3.0 Tesla: ω = 42.58 MHz/T × 3.0 T = 127.74 MHz .
9. An RF pulse transmitted with a strength and duration sufficient to flip the net
magnetization vector from the Z axis to the XY plane is a(n):
A. 90-degree pulse
B. 180-degree pulse
C. Inversion pulse
D. Gradient pulse
Answer: A
Explanation: A 90° RF pulse tips the net magnetization from the longitudinal to the
transverse plane, where it precesses and induces a detectable signal in the receiver coil .
10. An MR signal is generated when the net magnetization vector is:
A. Along the Z axis
B. At equilibrium
C. Some value greater than zero in the XY plane
D. Completely dephased
Answer: C
Explanation: The MR signal is induced when there is transverse magnetization (Mxy)
precessing in the XY plane. When Mxy is zero, no signal is generated .
11. Following the excitation pulse, the FID decays:
A. Linearly
B. Exponentially
C. During the 180-degree RF pulse
D. Along the Z axis
Answer: B
Explanation: The free induction decay (FID) signal decays exponentially due to T2*
dephasing as the transverse magnetization loses phase coherence .
12. The MR signal is strongest when the precessing nuclei are:
A. In phase coherence
B. Out of phase
C. Aligned with B₀
D. At equilibrium
Answer: A
Explanation: When precessing nuclei are in phase coherence, their individual signals add
together to produce a strong net signal. Dephasing causes signal loss .
