CAMRT /CAMRT-MRI EXAM 2025
QUESTIONS AND ANSWERS
Is SNR proportional or inversely proportional to voxel volume - ANS Proportional
3 fields used in MRI - ANS -static magnetic field
-TVMF (gradient field)
-RF field
3 main types of magnets used - ANS -Superconducting (most common_
-Resistive
-Permanent
FDA limits for the 3 fields in MRI - ANS Static field: 2T
TVMF: 3T/s
RF field:
- does not cause an increase in temperature of more than .5 deg C or any body part of 1 deg C
-SAR does not exceed 1W/kg avg over 25% of whole body for longer than 15mins
-SAR does not exceed 2W/kg avg over 25% of whole body for durations of 15mins or less
Eddy currents are caused by - ANS TVMF (gradients)
What are Eddy Currents - ANS Small currents induced in the body via the TVMF
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,Biological effects of the TVMF - ANS -Fibrillation
-Electroshock
-Visual phosphenes
-Peripheral nerve stimulation
SAR meaning and units - ANS Specific Absorption Rate
W/kg- Watts/kilogram
Which field is responsible for tissue heating and temperature increase - ANS The RF field
How are cardiac pacemakers affected in MRI - ANS Affected by all 3 fields
-Static field affects the operation and also exerts torque
-TVMF and RF field can interfere with circuitry
3 types of ferromagnetic materials? - ANS iron, cobalt, nickel
Level 1 MR Personnel - ANS Passed MR safety education requirements
Level 2 MR Personnel - ANS Those more extensively trained and educated in MRI safety
How many times should a non emergent patient be screened - ANS Twice, once verbally with
a level 2 MR Tech
How should emergent patients and their non MR personnel be screened - ANS Once
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, How should unconscious/ unresponsive patients be screened - ANS - A family member
should fill out the screening form
-If no reliable history can be obtained and MR exam cannot wait they must undergo plain film
radiography of head/neck, chest, abdomen/pelvis, upper arms and thighs
How should children and teens be screened - ANS Twice, once in front of parents and once
without
MRI and pregnant patients - ANS No known harmful effects but risk vs benefit assessment
should be made
MRI contrast and pregnant patients - ANS Should not be routinely given to pregnant patients
but risk vs benefit assessment needed
What is the spatial field gradient - ANS The variance in the fixed static field surrounding the
scanner, the manufacturerer supplies a SFG map
Lenz forces - ANS Faradays law states that a changing magnetic field will induce a current in a
conductor, Lenzs law states that the induced current will generate a secondary field that
opposes the original field
TVMF (gradient) effects - ANS -Induced voltages
-Auditory considerations
Normal temperature ranges - ANS Adult: 36.7-37.4 C
Child (4-13): 36.7-37 C
Infant (3mo-3yrs): 37.2-37.7 C
Normal pulse ranges - ANS Adult: 60-90 bpm
Child (4-10): 90-100 bpm
Infant: 120 bpm
3 Copyright ©BRIGHSTARS ALL RIGHTS RESERVED 2025
QUESTIONS AND ANSWERS
Is SNR proportional or inversely proportional to voxel volume - ANS Proportional
3 fields used in MRI - ANS -static magnetic field
-TVMF (gradient field)
-RF field
3 main types of magnets used - ANS -Superconducting (most common_
-Resistive
-Permanent
FDA limits for the 3 fields in MRI - ANS Static field: 2T
TVMF: 3T/s
RF field:
- does not cause an increase in temperature of more than .5 deg C or any body part of 1 deg C
-SAR does not exceed 1W/kg avg over 25% of whole body for longer than 15mins
-SAR does not exceed 2W/kg avg over 25% of whole body for durations of 15mins or less
Eddy currents are caused by - ANS TVMF (gradients)
What are Eddy Currents - ANS Small currents induced in the body via the TVMF
1 Copyright ©BRIGHSTARS ALL RIGHTS RESERVED 2025
,Biological effects of the TVMF - ANS -Fibrillation
-Electroshock
-Visual phosphenes
-Peripheral nerve stimulation
SAR meaning and units - ANS Specific Absorption Rate
W/kg- Watts/kilogram
Which field is responsible for tissue heating and temperature increase - ANS The RF field
How are cardiac pacemakers affected in MRI - ANS Affected by all 3 fields
-Static field affects the operation and also exerts torque
-TVMF and RF field can interfere with circuitry
3 types of ferromagnetic materials? - ANS iron, cobalt, nickel
Level 1 MR Personnel - ANS Passed MR safety education requirements
Level 2 MR Personnel - ANS Those more extensively trained and educated in MRI safety
How many times should a non emergent patient be screened - ANS Twice, once verbally with
a level 2 MR Tech
How should emergent patients and their non MR personnel be screened - ANS Once
2 Copyright ©BRIGHSTARS ALL RIGHTS RESERVED 2025
, How should unconscious/ unresponsive patients be screened - ANS - A family member
should fill out the screening form
-If no reliable history can be obtained and MR exam cannot wait they must undergo plain film
radiography of head/neck, chest, abdomen/pelvis, upper arms and thighs
How should children and teens be screened - ANS Twice, once in front of parents and once
without
MRI and pregnant patients - ANS No known harmful effects but risk vs benefit assessment
should be made
MRI contrast and pregnant patients - ANS Should not be routinely given to pregnant patients
but risk vs benefit assessment needed
What is the spatial field gradient - ANS The variance in the fixed static field surrounding the
scanner, the manufacturerer supplies a SFG map
Lenz forces - ANS Faradays law states that a changing magnetic field will induce a current in a
conductor, Lenzs law states that the induced current will generate a secondary field that
opposes the original field
TVMF (gradient) effects - ANS -Induced voltages
-Auditory considerations
Normal temperature ranges - ANS Adult: 36.7-37.4 C
Child (4-13): 36.7-37 C
Infant (3mo-3yrs): 37.2-37.7 C
Normal pulse ranges - ANS Adult: 60-90 bpm
Child (4-10): 90-100 bpm
Infant: 120 bpm
3 Copyright ©BRIGHSTARS ALL RIGHTS RESERVED 2025
