ASMIRT – MRI Accreditation Exam
With Questions And Answers Updated
2026/2027|Graded A+
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 (i.e. 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 liter of liquid helium expands to 760 liters 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 vapor pressure exceeds a predetermined value, the vent-bursting disk on the vent pipe
ruptures and ventilates the excess vapor. 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
magnetization 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 magnetization 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 magnetization
vector? - ANSWER>This situation is changed in the presence of a stationary magnetic field (Bo) which
induces some of the magnetic moments of the protons to align in its direction, partially overcoming
thermal randomization and producing a net magnetization 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
With Questions And Answers Updated
2026/2027|Graded A+
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 (i.e. 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 liter of liquid helium expands to 760 liters 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 vapor pressure exceeds a predetermined value, the vent-bursting disk on the vent pipe
ruptures and ventilates the excess vapor. 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
magnetization 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 magnetization 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 magnetization
vector? - ANSWER>This situation is changed in the presence of a stationary magnetic field (Bo) which
induces some of the magnetic moments of the protons to align in its direction, partially overcoming
thermal randomization and producing a net magnetization 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
