1|Page
ASMIRT MRI ACCREDITATION ACTUAL
EXAM PREP 2026 ALL QUESTIONS AND
CORRECT DETAILED ANSWERS ALREADY
A GRADED WITH EXPERT FEEDBACK
|NEW AND REVISED
What determines whether a hydrogen proton will align parallel or
antiparallel? - ANSWER- A hydrogen proton will align parallel or
antiparallel dependent upon the relative energy of the individual proton
and also the strength of the main magnetic field. Protons with lower
energy align parallel and those with higher energy align antiparallel
Does a stronger or weaker field result in fewer protons being able to
align anti-parallel? - ANSWER- The stronger the field the fewer protons
are able to align antiparallel.
Before a sample is introduced to the main magnetic field, explain what is
happening in terms of the net magnetisation vector? - ANSWER- A
good way to think about the NMV is to take the example of a single
voxel of tissue. A voxel contains many protons with the net
magnetisation vector (M) being the vector sum of the individual protons.
In the absence of a magnetic field, the spatial orientation of each protons
magnetic moment is random and M = 0
When a sample is introduced to the main magnetic field, explain what
happens to the net magnetisation vector? - ANSWER- This situation is
changed in the presence of a stationary magnetic field (Bo) which
,2|Page
induces some of the magnetic moments of the protons to align in its
direction, partially overcoming thermal randomisation and producing a
net magnetisation in the direction of Bo
What forms the NMV? - ANSWER- • The presence of B0 creates an
abundance of protons in alignment with this field.
• It is this abundance of protons which forms the NMV
What is precession? - ANSWER- Each hydrogen nucleus that makes up
the NMV is spinning on its own axis as shown in the diagram. The
influence of the static magnetic field B0 creates an additional spin of the
NMV around B0. This secondary spin is called precession and causes
the magnetic moments to follow a circular path around B0.
What is precessional frequency and what is it measured in? - ANSWER-
The speed at which the NMV rotates around B0 is called the
precessional frequency. It is measured in megahertz (MHZ). Where one
cycle per second is 1Hz.
The value of the precessional frequency is governed by the _________
_____________: - ANSWER- Larmor frequency
What is the Larmor frequency? - ANSWER- The precessional frequency
(ω0) = B0 × y
Where by B0 is the magnetic field strength of the magnet, and y is the
gyromagnetic ratio.
,3|Page
What is the gyromagnetic ratio? - ANSWER- The gyromagnetic ratio of
hydrogen is 42.57 MHz/T at 1.0T field strength. The gyromagnetic ratio
is a constant for each type of nucleus however field strengths are
variable and as such the precessional frequency for each nucleus will be
different dependent on the strength of the magnet.
What is resonance? - ANSWER- Resonance is a phenomenon that
occurs when an object is exposed to an oscillating perturbation that has a
frequency close to its own natural frequency of oscillation. In MR a
hydrogen nucleus will gain energy and resonate if the energy is
delivered at exactly its precessional frequency. If the energy is delivered
to the nucleus at a different frequency to that of the Larmor frequency of
the nucleus resonance will not occur.
What is flip angle? - ANSWER- The result of resonance is that the
NMV moves out of alignment from B0. The angle to which the NMV
moves out of alignment is known as the flip angle. The magnitude of the
flip angle depends upon the amplitude and duration of the RF pulse.
Typically the flip angle is 90 degrees.
With a flip angle of 90 degrees, what happens to the NMV? -
ANSWER- With a flip angle of 90 degrees the result is that the NMV
moves away from B0 and is completely transferred into the transverse
plane
Besides moving the NMV, what additional effect does resonance have
on the magnetic movement of hydrogen protons? - ANSWER- The
second result of resonance is that the magnetic moments of the hydrogen
, 4|Page
protons move into phase with each other. That is all of the protons are in
the same position of the precessional path.
What physical law, forms the basis on MRI signal generation? -
ANSWER- According to Faraday's law of induction, a changing
magnetic field will generate a voltage in a suitably located receiver coil.
This is the basis of signal detection in MRI
How is signal detected in MRI? - ANSWER- For a signal to be detected,
the magnetisation induced by Bo in the direction of Bo needs to be
converted into a magnetisation which precesses in the X-Y plane. This is
done by applying a RF pulse (B1) that causes the NMV to flip and
precess in the transverse plane. NMV will precess about B1 which can
be pulsed for as long as it takes to rotate the magnetisation through 90
degrees into the transverse plane. Individual protons will now be
precessing in phase to produce a rotating magnetisation which can be
detected with a receiver coil.
What happens to MRI signal over time and what is this called? -
ANSWER- When a scanning sequence starts, the magnetisation in the
longitudinal plane is flipped into the transverse plane using an RF pulse.
This creates a measurable signal in the receiver coil. Over time this
signal fades away or decays. This is known as relaxation of the signal.
After the RF pulse, the NMV moves back towards the longitudinal plane
via two relaxation processes.
What are the two types of relaxation in MRI? - ANSWER- • Spin-
Lattice Relaxation, T1 Relaxation
• Spin-Spin Relaxation, T2 Relaxation or T2 decay
ASMIRT MRI ACCREDITATION ACTUAL
EXAM PREP 2026 ALL QUESTIONS AND
CORRECT DETAILED ANSWERS ALREADY
A GRADED WITH EXPERT FEEDBACK
|NEW AND REVISED
What determines whether a hydrogen proton will align parallel or
antiparallel? - ANSWER- A hydrogen proton will align parallel or
antiparallel dependent upon the relative energy of the individual proton
and also the strength of the main magnetic field. Protons with lower
energy align parallel and those with higher energy align antiparallel
Does a stronger or weaker field result in fewer protons being able to
align anti-parallel? - ANSWER- The stronger the field the fewer protons
are able to align antiparallel.
Before a sample is introduced to the main magnetic field, explain what is
happening in terms of the net magnetisation vector? - ANSWER- A
good way to think about the NMV is to take the example of a single
voxel of tissue. A voxel contains many protons with the net
magnetisation vector (M) being the vector sum of the individual protons.
In the absence of a magnetic field, the spatial orientation of each protons
magnetic moment is random and M = 0
When a sample is introduced to the main magnetic field, explain what
happens to the net magnetisation vector? - ANSWER- This situation is
changed in the presence of a stationary magnetic field (Bo) which
,2|Page
induces some of the magnetic moments of the protons to align in its
direction, partially overcoming thermal randomisation and producing a
net magnetisation in the direction of Bo
What forms the NMV? - ANSWER- • The presence of B0 creates an
abundance of protons in alignment with this field.
• It is this abundance of protons which forms the NMV
What is precession? - ANSWER- Each hydrogen nucleus that makes up
the NMV is spinning on its own axis as shown in the diagram. The
influence of the static magnetic field B0 creates an additional spin of the
NMV around B0. This secondary spin is called precession and causes
the magnetic moments to follow a circular path around B0.
What is precessional frequency and what is it measured in? - ANSWER-
The speed at which the NMV rotates around B0 is called the
precessional frequency. It is measured in megahertz (MHZ). Where one
cycle per second is 1Hz.
The value of the precessional frequency is governed by the _________
_____________: - ANSWER- Larmor frequency
What is the Larmor frequency? - ANSWER- The precessional frequency
(ω0) = B0 × y
Where by B0 is the magnetic field strength of the magnet, and y is the
gyromagnetic ratio.
,3|Page
What is the gyromagnetic ratio? - ANSWER- The gyromagnetic ratio of
hydrogen is 42.57 MHz/T at 1.0T field strength. The gyromagnetic ratio
is a constant for each type of nucleus however field strengths are
variable and as such the precessional frequency for each nucleus will be
different dependent on the strength of the magnet.
What is resonance? - ANSWER- Resonance is a phenomenon that
occurs when an object is exposed to an oscillating perturbation that has a
frequency close to its own natural frequency of oscillation. In MR a
hydrogen nucleus will gain energy and resonate if the energy is
delivered at exactly its precessional frequency. If the energy is delivered
to the nucleus at a different frequency to that of the Larmor frequency of
the nucleus resonance will not occur.
What is flip angle? - ANSWER- The result of resonance is that the
NMV moves out of alignment from B0. The angle to which the NMV
moves out of alignment is known as the flip angle. The magnitude of the
flip angle depends upon the amplitude and duration of the RF pulse.
Typically the flip angle is 90 degrees.
With a flip angle of 90 degrees, what happens to the NMV? -
ANSWER- With a flip angle of 90 degrees the result is that the NMV
moves away from B0 and is completely transferred into the transverse
plane
Besides moving the NMV, what additional effect does resonance have
on the magnetic movement of hydrogen protons? - ANSWER- The
second result of resonance is that the magnetic moments of the hydrogen
, 4|Page
protons move into phase with each other. That is all of the protons are in
the same position of the precessional path.
What physical law, forms the basis on MRI signal generation? -
ANSWER- According to Faraday's law of induction, a changing
magnetic field will generate a voltage in a suitably located receiver coil.
This is the basis of signal detection in MRI
How is signal detected in MRI? - ANSWER- For a signal to be detected,
the magnetisation induced by Bo in the direction of Bo needs to be
converted into a magnetisation which precesses in the X-Y plane. This is
done by applying a RF pulse (B1) that causes the NMV to flip and
precess in the transverse plane. NMV will precess about B1 which can
be pulsed for as long as it takes to rotate the magnetisation through 90
degrees into the transverse plane. Individual protons will now be
precessing in phase to produce a rotating magnetisation which can be
detected with a receiver coil.
What happens to MRI signal over time and what is this called? -
ANSWER- When a scanning sequence starts, the magnetisation in the
longitudinal plane is flipped into the transverse plane using an RF pulse.
This creates a measurable signal in the receiver coil. Over time this
signal fades away or decays. This is known as relaxation of the signal.
After the RF pulse, the NMV moves back towards the longitudinal plane
via two relaxation processes.
What are the two types of relaxation in MRI? - ANSWER- • Spin-
Lattice Relaxation, T1 Relaxation
• Spin-Spin Relaxation, T2 Relaxation or T2 decay
