ASMIRT- MRI Accreditation Actual Exam
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Accreditation Exam Preparation /ASMIRT-
MRI Accreditation Practice Exam With
Questions And Correct Detailed Answers
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Mild sensory effects due to static magnetic fields include: - ANSWER>>• Vertigo
• Nausea
• Taste Sensations
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
• conductivity of the tissue
What determines the SAR calculation? - ANSWER>>The SAR is calculated for each
sequence on the basis of the sequence parameters and the patient weight
What are the FDA recommendations regarding SAR? - ANSWER>>• 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
Why is patient heating a concern in MRI? - ANSWER>>• 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.
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? - ANSWER>>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
How can patient burns be avoided? - ANSWER>>• 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
Explain the deleterious effects of MRI on pregnant patients - ANSWER>>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.
Can pregnant staff enter the MRI environment? - ANSWER>>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.
Is contrast recommended in pregnant patients? - ANSWER>>Contrast is not
recommended during pregnancy. It has been shown to cross the placenta.
What is a quench? - ANSWER>>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 scan room. It may become
impossible to open an inward opening door due to the pressure differential. In
this case kick out panels should be used to reduce the pressure differential and
allow opening of the door. In the absence of these panels the scan room window
should be broken to allow access to the patient if necessary.
When placed inside a magnetic field the hydrogen protons within the human
body will: - ANSWER>>Will attempt to align with the main magnetic field (B0)
The hydrogen proton due to the presence of its single positively charged proton
can align in how many directions - ANSWER>>Two (parallel or anti-parallel)
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
Test Bank Newest / ASMIRT- MRI
Accreditation Exam Preparation /ASMIRT-
MRI Accreditation Practice Exam With
Questions And Correct Detailed Answers
|Already Graded A+(Newest Version!)
Mild sensory effects due to static magnetic fields include: - ANSWER>>• Vertigo
• Nausea
• Taste Sensations
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
• conductivity of the tissue
What determines the SAR calculation? - ANSWER>>The SAR is calculated for each
sequence on the basis of the sequence parameters and the patient weight
What are the FDA recommendations regarding SAR? - ANSWER>>• 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
Why is patient heating a concern in MRI? - ANSWER>>• 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.
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? - ANSWER>>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
How can patient burns be avoided? - ANSWER>>• 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
Explain the deleterious effects of MRI on pregnant patients - ANSWER>>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.
Can pregnant staff enter the MRI environment? - ANSWER>>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.
Is contrast recommended in pregnant patients? - ANSWER>>Contrast is not
recommended during pregnancy. It has been shown to cross the placenta.
What is a quench? - ANSWER>>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 scan room. It may become
impossible to open an inward opening door due to the pressure differential. In
this case kick out panels should be used to reduce the pressure differential and
allow opening of the door. In the absence of these panels the scan room window
should be broken to allow access to the patient if necessary.
When placed inside a magnetic field the hydrogen protons within the human
body will: - ANSWER>>Will attempt to align with the main magnetic field (B0)
The hydrogen proton due to the presence of its single positively charged proton
can align in how many directions - ANSWER>>Two (parallel or anti-parallel)
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
