ASMIRT - MRI Accreditation Australian Society of Medical Imaging and Rad
ation Therapy (ASMIRT)
Study online at https://quizlet.com/_j3f6il
1. ASMIRT - MRI Accreditation: EXAM COVERAGE - ASMIRT MRI Accreditation
The MRI Accreditation by Australian Society of Medical Imaging and Radiation Therapy (ASMIRT) evaluates professional
knowledge and competency in Magnetic Resonance Imaging (MRI) practice. The exam covers MRI physics principles,
image formation, pulse sequences, and safety protocols related to magnetic fields and radiofrequency exposure. It also
includes patient preparation and positioning, contrast media use, MRI equipment operation, and quality assurance
procedures. Additional areas include cross-sectional anatomy, pathology recognition on MRI images, infection control,
and professional and ethical standards in medical imaging practice. The exam emphasizes safe MRI operation, accurate
image acquisition, patient care, and adherence to clinical and regulatory standards in diagnostic imaging.
2. Sensory effects of the static magnetic field increase or decrease with field
strength?: 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
3. Explain what t-wave artefact is and why it occurs: 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 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.
4. Mild sensory effects due to static magnetic fields include:: • Vertigo
• Nausea
• Taste Sensations
5. What risks does the static magnetic field pose in terms of implants and
objects?: 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.
6. What strategies can be employed to reduce the risks of the static magnetic
field impacting on implants and objects?: • 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. •
, ASMIRT - MRI Accreditation Australian Society of Medical Imaging and Rad
ation Therapy (ASMIRT)
Study online at https://quizlet.com/_j3f6il
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.
7. What effect do gradient magnetic fields have on patient safety?: 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 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
8. What strategies can be employed to keep gradient effects to a minimum?: 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
9. What is the cause of acoustic noise during an MRI scan?: 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 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.
10. What is the greatest concern in terms of MR safety?: 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.
, ASMIRT - MRI Accreditation Australian Society of Medical Imaging and Rad
ation Therapy (ASMIRT)
Study online at https://quizlet.com/_j3f6il
11. RF field safety concerns increase or decrease with increasing field strength>-
: The amount of energy absorbed will increase with frequency of the RF field delivered and is therefore greater at higher
field strengths
12. What is SAR?: SAR= Specific Absorption Rate - the term used to describe energy dissipation
13. SAR is expressed in:: Watts / kg
14. SAR will depend on factors including:: • 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
• conductivity of the tissue
15. What determines the SAR calculation?: The SAR is calculated for each sequence on the basis of
the sequence parameters and the patient weight
16. What are the FDA recommendations regarding SAR?: • Maximum SAR of 0.4 W/kg (whole
body)
• 3.2 W/kg (head)
• 8.0 W/kg (in any one gram of tissue)
• RF exposure should be insufficient to produce a core temperature increase of 1 degree C
17. Why is patient heating a concern in MRI?: • Heating will also vary with the state of the patient's
thermo-regulatory system, the ambient temperature, the humidity and the air flow around the patient.
• The eye and the testes are particularly sensitive organs due to a low capacity for heat dissipation.
• Excessive RF exposure and temperature increase can lead to an increase in blood pressure and heart rate.
18. A SAR warning appears during a scan preventing you from continuing with
an examination unless factors are altered to a safe level, what can be changed
in order to achieve this?: Factors which will reduce SAR if required include:
• reducing the number of slices
• reducing the ETL
• increasing the TR
• GE rather than SE
• Use quadrature coils rather than linear coils for transmission
• Change to low SAR sequence design
, ASMIRT - MRI Accreditation Australian Society of Medical Imaging and Rad
ation Therapy (ASMIRT)
Study online at https://quizlet.com/_j3f6il
19. How can patient burns be avoided?: • use only equipment tested to be MR compatible
• allow only MR trained staff to use the equipment
• check the integrity of the electrical insulation of all cables
• remove all unnecessary electrically conductive equipment from the bore
• keep electrically conductive equipment from directly contacting the patient
• keep electrically conductive equipment from forming large diameter conductive loops
• position cables to avoid cross points
• position ECG cables to exit down the centre of the bore
• do not allow contact between the patient's skin and the magnet bore
20. Explain the deleterious effects of MRI on pregnant patients: There are no known
biological effects of MRI on foetuses. MR imaging may be used in pregnant women if other non-ionizing forms of
diagnostic imaging are inadequate or if the examination provides important information that would otherwise require
exposure to ionizing radiation (e.g., fluoroscopy, CT, etc.). Pregnant patients should be informed that, to date, there has
been no indication that the use of clinical MR imaging during pregnancy has produced deleterious effects." This policy
has been adopted by the American College of Radiology and is considered to be the "standard of care" with respect
to the use of MRI procedures in pregnant patients. Importantly, this information applies to MR systems operating up
to and including 3-Tesla. (MR Imaging Safety and Patient Management issued by the Safety Committee of the Society
for Magnetic Resonance Imaging) Pregnant patients should be reviewed on a case by case basis to assess whether the
risks outweigh the potential benefits.
21. Can pregnant staff enter the MRI environment?: No increased incidence of spontaneous
abortion has been demonstrated among MR radiographers or nurses. The most common policy seems to be that
pregnant staff are allowed exposure to the static field (ie. to set patients up) but leave the room during image acquisition
to avoid exposure to RF and gradient fields.
22. Is contrast recommended in pregnant patients?: Contrast is not recommended during
pregnancy. It has been shown to cross the placenta.
23. What is a quench?: Quenching the magnet results in a large amount of helium gas boil off from liquid
helium inside the magnet. One litre of liquid helium expands to 760 litres of helium gas. During a quench, the liquid
helium is heated causing it to boil off. The quench pipe vents the resultant gas outside. If the vapour pressure exceeds
a predetermined value, the vent-bursting disk on the vent pipe ruptures and ventilates the excess vapour. Some may
enter the scan room reducing oxygen levels. Helium gas displaces oxygen and is hard to detect until it is too late.
Asphyxia is possible due to low oxygen levels. Another concern is the increase in pressure due to helium flooding the
ation Therapy (ASMIRT)
Study online at https://quizlet.com/_j3f6il
1. ASMIRT - MRI Accreditation: EXAM COVERAGE - ASMIRT MRI Accreditation
The MRI Accreditation by Australian Society of Medical Imaging and Radiation Therapy (ASMIRT) evaluates professional
knowledge and competency in Magnetic Resonance Imaging (MRI) practice. The exam covers MRI physics principles,
image formation, pulse sequences, and safety protocols related to magnetic fields and radiofrequency exposure. It also
includes patient preparation and positioning, contrast media use, MRI equipment operation, and quality assurance
procedures. Additional areas include cross-sectional anatomy, pathology recognition on MRI images, infection control,
and professional and ethical standards in medical imaging practice. The exam emphasizes safe MRI operation, accurate
image acquisition, patient care, and adherence to clinical and regulatory standards in diagnostic imaging.
2. Sensory effects of the static magnetic field increase or decrease with field
strength?: 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
3. Explain what t-wave artefact is and why it occurs: 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 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.
4. Mild sensory effects due to static magnetic fields include:: • Vertigo
• Nausea
• Taste Sensations
5. What risks does the static magnetic field pose in terms of implants and
objects?: 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.
6. What strategies can be employed to reduce the risks of the static magnetic
field impacting on implants and objects?: • 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. •
, ASMIRT - MRI Accreditation Australian Society of Medical Imaging and Rad
ation Therapy (ASMIRT)
Study online at https://quizlet.com/_j3f6il
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.
7. What effect do gradient magnetic fields have on patient safety?: 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 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
8. What strategies can be employed to keep gradient effects to a minimum?: 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
9. What is the cause of acoustic noise during an MRI scan?: 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 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.
10. What is the greatest concern in terms of MR safety?: 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.
, ASMIRT - MRI Accreditation Australian Society of Medical Imaging and Rad
ation Therapy (ASMIRT)
Study online at https://quizlet.com/_j3f6il
11. RF field safety concerns increase or decrease with increasing field strength>-
: The amount of energy absorbed will increase with frequency of the RF field delivered and is therefore greater at higher
field strengths
12. What is SAR?: SAR= Specific Absorption Rate - the term used to describe energy dissipation
13. SAR is expressed in:: Watts / kg
14. SAR will depend on factors including:: • 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
• conductivity of the tissue
15. What determines the SAR calculation?: The SAR is calculated for each sequence on the basis of
the sequence parameters and the patient weight
16. What are the FDA recommendations regarding SAR?: • Maximum SAR of 0.4 W/kg (whole
body)
• 3.2 W/kg (head)
• 8.0 W/kg (in any one gram of tissue)
• RF exposure should be insufficient to produce a core temperature increase of 1 degree C
17. Why is patient heating a concern in MRI?: • Heating will also vary with the state of the patient's
thermo-regulatory system, the ambient temperature, the humidity and the air flow around the patient.
• The eye and the testes are particularly sensitive organs due to a low capacity for heat dissipation.
• Excessive RF exposure and temperature increase can lead to an increase in blood pressure and heart rate.
18. A SAR warning appears during a scan preventing you from continuing with
an examination unless factors are altered to a safe level, what can be changed
in order to achieve this?: Factors which will reduce SAR if required include:
• reducing the number of slices
• reducing the ETL
• increasing the TR
• GE rather than SE
• Use quadrature coils rather than linear coils for transmission
• Change to low SAR sequence design
, ASMIRT - MRI Accreditation Australian Society of Medical Imaging and Rad
ation Therapy (ASMIRT)
Study online at https://quizlet.com/_j3f6il
19. How can patient burns be avoided?: • use only equipment tested to be MR compatible
• allow only MR trained staff to use the equipment
• check the integrity of the electrical insulation of all cables
• remove all unnecessary electrically conductive equipment from the bore
• keep electrically conductive equipment from directly contacting the patient
• keep electrically conductive equipment from forming large diameter conductive loops
• position cables to avoid cross points
• position ECG cables to exit down the centre of the bore
• do not allow contact between the patient's skin and the magnet bore
20. Explain the deleterious effects of MRI on pregnant patients: There are no known
biological effects of MRI on foetuses. MR imaging may be used in pregnant women if other non-ionizing forms of
diagnostic imaging are inadequate or if the examination provides important information that would otherwise require
exposure to ionizing radiation (e.g., fluoroscopy, CT, etc.). Pregnant patients should be informed that, to date, there has
been no indication that the use of clinical MR imaging during pregnancy has produced deleterious effects." This policy
has been adopted by the American College of Radiology and is considered to be the "standard of care" with respect
to the use of MRI procedures in pregnant patients. Importantly, this information applies to MR systems operating up
to and including 3-Tesla. (MR Imaging Safety and Patient Management issued by the Safety Committee of the Society
for Magnetic Resonance Imaging) Pregnant patients should be reviewed on a case by case basis to assess whether the
risks outweigh the potential benefits.
21. Can pregnant staff enter the MRI environment?: No increased incidence of spontaneous
abortion has been demonstrated among MR radiographers or nurses. The most common policy seems to be that
pregnant staff are allowed exposure to the static field (ie. to set patients up) but leave the room during image acquisition
to avoid exposure to RF and gradient fields.
22. Is contrast recommended in pregnant patients?: Contrast is not recommended during
pregnancy. It has been shown to cross the placenta.
23. What is a quench?: Quenching the magnet results in a large amount of helium gas boil off from liquid
helium inside the magnet. One litre of liquid helium expands to 760 litres of helium gas. During a quench, the liquid
helium is heated causing it to boil off. The quench pipe vents the resultant gas outside. If the vapour pressure exceeds
a predetermined value, the vent-bursting disk on the vent pipe ruptures and ventilates the excess vapour. Some may
enter the scan room reducing oxygen levels. Helium gas displaces oxygen and is hard to detect until it is too late.
Asphyxia is possible due to low oxygen levels. Another concern is the increase in pressure due to helium flooding the
