1|Page
ASMIRT - MRI ACCREDITATION
ACTUAL EXAM PREP 2026 ALL
QUESTIONS AND CORRECT
DETAILED ANSWERS ALREADY A
GRADED WITH EXPERT FEEDBACK
|NEW AND REVISED
Mild sensory effects due to static magnetic fields include: - ANSWER- •
Vertigo
• Nausea
• Taste Sensations
Sensory effects of the static magnetic field increase or decrease with
field strength? - ANSWER- Sensory effects are related to the strength of
the magnetic field with few symptoms at 1.5T and more appearing
approaching a 4T field strength
Explain what t-wave artefact is and why it occurs - ANSWER- Any
charged particle moving through a magnetic field will have a current
induced via this interaction. As blood, a conductive fluid flows through a
magnetic field it induces an electrical biopotential. This electrical
biopotential can be seen on the ECG waveform of patients in MRI. It is
demonstrated by an increase in the T-wave amplitude on ECG. This
change in T-wave amplitude is directly proportional to the strength of
,2|Page
the Static Filed. It is important that MR radiographers are aware of this
as elevated T-waves are also associated with ischemia and myocardial
infarction.
What risks does the static magnetic field pose in terms of implants and
objects? - ANSWER- Static Fields also pose hazards through the
displacement of ferro-magnetic implants and objects. The static field
imparts both a translation (attractive force) and a torque (twisting force).
The strong nature of the Static Field also has the potential to disrupt the
function of Cardiac Pacemakers. Anyone entering beyond the 5G line
should be screened for contraindications to strong Magnetic Fields. Also
be aware of what is being taken over the 5G line.
What strategies can be employed to reduce the risks of the static
magnetic field impacting on implants and objects? - ANSWER- •
Ferromagnetic objects may become airborne - 40 km/hr terminal
velocity possible at 1.5T
• Test any metal objects with a hand held magnet before allowing them
to enter the room.
• Keep the general public behind the 5G line. •
Possible contra-indications include pacemakers, aneurysm clips, intra-
vascular coils and stents, heart valves, penile implants, cochlear
implants, ocular implants (Fatio eyelid springs), neuro stimulators, bone
growth stimulators, drug infusion pumps.
What effect do gradient magnetic fields have on patient safety? -
ANSWER- Faraday's Law dictates that changing magnetic fields will
generate a voltage and a current in a conductor. The switching of the
gradients induces electrical currents in conductive tissues. Voltage
,3|Page
generation will occur during the rise and fall times - ie. while the field is
changing. The largest voltages will be generated at the periphery where
the gradient amplitudes are highest. The most common result of these
voltages is Peripheral Nerve Stimulation (PNS). Other side-effects are
listed below;
• magnetophosphenes - electromagnetically induced flashes of light
• seizures
• tissue heating
• peripheral nerve stimulation
• muscle contractions
• cardiac arrhythmias
• some degree of patient heating has been shown to be a result of
Gradient Magnetic effects. However, this has been shown to be so low
as to be negligible
What strategies can be employed to keep gradient effects to a minimum?
- ANSWER- In order to keep these effects to a minimum the following
is recommended.
• keep dB/dT less than those required to produce peripheral nerve
stimulation.
• max limit for dB/dT of 6 Tesla / sec
What is the cause of acoustic noise during an MRI scan? - ANSWER-
The characteristic noise that is heard during an MRI scan is the result of
the interaction of Lorentz forces generated by the Gradient Coil when a
current is pulsed through them in the presence of a Static Magnetic
Field. The noise results as these forces are so strong as to twist the coils
, 4|Page
on their mounts. In some cases this can be in excess of 100dB
particularly when running EPI sequences. Thus all patients need to be
provided hearing protection.
What is the greatest concern in terms of MR safety? - ANSWER- RF
effects are of the greatest concern in terms of MR safety. The main
effect is the deposition of energy resulting in tissue heating. Of
particular concern are heat sensitive organs such as the eyes and testes.
One of the major concerns is where a patient has a metallic implant
which results in greater heating.
RF field safety concerns increase or decrease with increasing field
strength> - ANSWER- The amount of energy absorbed will increase
with frequency of the RF field delivered and is therefore greater at
higher field strengths
What is SAR? - ANSWER- SAR= Specific Absorption Rate - the term
used to describe energy dissipation
SAR is expressed in: - ANSWER- Watts / kg
SAR will depend on factors including: - ANSWER- • frequency (&
therefore the field strength)
• RF pulse - where power deposited is proportional to (flip angle / 90)
• TR
• RF coil - transmit / receive or receive only
• volume of tissue within the coil
ASMIRT - MRI ACCREDITATION
ACTUAL EXAM PREP 2026 ALL
QUESTIONS AND CORRECT
DETAILED ANSWERS ALREADY A
GRADED WITH EXPERT FEEDBACK
|NEW AND REVISED
Mild sensory effects due to static magnetic fields include: - ANSWER- •
Vertigo
• Nausea
• Taste Sensations
Sensory effects of the static magnetic field increase or decrease with
field strength? - ANSWER- Sensory effects are related to the strength of
the magnetic field with few symptoms at 1.5T and more appearing
approaching a 4T field strength
Explain what t-wave artefact is and why it occurs - ANSWER- Any
charged particle moving through a magnetic field will have a current
induced via this interaction. As blood, a conductive fluid flows through a
magnetic field it induces an electrical biopotential. This electrical
biopotential can be seen on the ECG waveform of patients in MRI. It is
demonstrated by an increase in the T-wave amplitude on ECG. This
change in T-wave amplitude is directly proportional to the strength of
,2|Page
the Static Filed. It is important that MR radiographers are aware of this
as elevated T-waves are also associated with ischemia and myocardial
infarction.
What risks does the static magnetic field pose in terms of implants and
objects? - ANSWER- Static Fields also pose hazards through the
displacement of ferro-magnetic implants and objects. The static field
imparts both a translation (attractive force) and a torque (twisting force).
The strong nature of the Static Field also has the potential to disrupt the
function of Cardiac Pacemakers. Anyone entering beyond the 5G line
should be screened for contraindications to strong Magnetic Fields. Also
be aware of what is being taken over the 5G line.
What strategies can be employed to reduce the risks of the static
magnetic field impacting on implants and objects? - ANSWER- •
Ferromagnetic objects may become airborne - 40 km/hr terminal
velocity possible at 1.5T
• Test any metal objects with a hand held magnet before allowing them
to enter the room.
• Keep the general public behind the 5G line. •
Possible contra-indications include pacemakers, aneurysm clips, intra-
vascular coils and stents, heart valves, penile implants, cochlear
implants, ocular implants (Fatio eyelid springs), neuro stimulators, bone
growth stimulators, drug infusion pumps.
What effect do gradient magnetic fields have on patient safety? -
ANSWER- Faraday's Law dictates that changing magnetic fields will
generate a voltage and a current in a conductor. The switching of the
gradients induces electrical currents in conductive tissues. Voltage
,3|Page
generation will occur during the rise and fall times - ie. while the field is
changing. The largest voltages will be generated at the periphery where
the gradient amplitudes are highest. The most common result of these
voltages is Peripheral Nerve Stimulation (PNS). Other side-effects are
listed below;
• magnetophosphenes - electromagnetically induced flashes of light
• seizures
• tissue heating
• peripheral nerve stimulation
• muscle contractions
• cardiac arrhythmias
• some degree of patient heating has been shown to be a result of
Gradient Magnetic effects. However, this has been shown to be so low
as to be negligible
What strategies can be employed to keep gradient effects to a minimum?
- ANSWER- In order to keep these effects to a minimum the following
is recommended.
• keep dB/dT less than those required to produce peripheral nerve
stimulation.
• max limit for dB/dT of 6 Tesla / sec
What is the cause of acoustic noise during an MRI scan? - ANSWER-
The characteristic noise that is heard during an MRI scan is the result of
the interaction of Lorentz forces generated by the Gradient Coil when a
current is pulsed through them in the presence of a Static Magnetic
Field. The noise results as these forces are so strong as to twist the coils
, 4|Page
on their mounts. In some cases this can be in excess of 100dB
particularly when running EPI sequences. Thus all patients need to be
provided hearing protection.
What is the greatest concern in terms of MR safety? - ANSWER- RF
effects are of the greatest concern in terms of MR safety. The main
effect is the deposition of energy resulting in tissue heating. Of
particular concern are heat sensitive organs such as the eyes and testes.
One of the major concerns is where a patient has a metallic implant
which results in greater heating.
RF field safety concerns increase or decrease with increasing field
strength> - ANSWER- The amount of energy absorbed will increase
with frequency of the RF field delivered and is therefore greater at
higher field strengths
What is SAR? - ANSWER- SAR= Specific Absorption Rate - the term
used to describe energy dissipation
SAR is expressed in: - ANSWER- Watts / kg
SAR will depend on factors including: - ANSWER- • frequency (&
therefore the field strength)
• RF pulse - where power deposited is proportional to (flip angle / 90)
• TR
• RF coil - transmit / receive or receive only
• volume of tissue within the coil
