MRI CAMRT Exam Questions And 100%
Correct Answers
Is SNR proportional or inversely proportional to voxel volume - ANSWER Proportional
3 fields used in MRI - ANSWER -static magnetic field
-TVMF (gradient field)
-RF field
3 main types of magnets used - ANSWER -Superconducting (most common_
-Resistive
-Permanent
FDA limits for the 3 fields in MRI - ANSWER 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 - ANSWER TVMF (gradients)
What is Eddy Currents - ANSWER Small currents induced in the body via the TVMF
Biological effects of the TVMF - ANSWER -Fibrillation
,-Electroshock
-Visual phosphenes
-Peripheral nerve stimulation
SAR meaning and units - ANSWER Specific Absorption Rate
W/kg- Watts/kilogram
Which field is responsible for tissue heating and temperature increase - ANSWER The
RF field
How are cardiac pacemakers affected in MRI - ANSWER 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? - ANSWER iron, cobalt, nickel
Level 1 MR Personnel - ANSWER Passed MR safety education requirements
Level 2 MR Personnel - ANSWER Those more extensively trained and educated in MRI
safety
How many times should a non emergent patient be screened - ANSWER Twice, once
verbally with a level 2 MR Tech
How should emergent patients and their non MR personnel be screened - ANSWER
Once
, How should unconscious/ unresponsive patients be screened - ANSWER - 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 adolescents be screened?
ANSWER Twice, once in front of parents and once without
MRI and pregnant patients - ANSWER No known harmful effects but risk vs benefit
assessment should be made
MRI contrast and pregnant patients - ANSWER Should not be routinely given to pregnant
patients but risk vs benefit assessment needed
Spatial field gradient - ANSWER The fixed static field varies around the scanner, the
manufacturerer will provide a SFG map
Lenz forces - ANSWER Faradays law, a time varying magnetic field will induce a current
within a conductor, Lenzs law, the induced current within the conductor will create a
secondary field that acts in the opposite direction of the original field
TVMF (gradient) effects - ANSWER -Induced voltages
-Auditory considerations
Normal Temperature Ranges -ANSWER Adult: 36.7-37.4 C
Child (4-13): 36.7-37 C
Infant (3 mo-3 yrs.): 37.2-37.7 C
Normal Pulse Ranges -ANSWER Adult : 60-90 bpm
Child (4-10): 90-100 bpm
Correct Answers
Is SNR proportional or inversely proportional to voxel volume - ANSWER Proportional
3 fields used in MRI - ANSWER -static magnetic field
-TVMF (gradient field)
-RF field
3 main types of magnets used - ANSWER -Superconducting (most common_
-Resistive
-Permanent
FDA limits for the 3 fields in MRI - ANSWER 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 - ANSWER TVMF (gradients)
What is Eddy Currents - ANSWER Small currents induced in the body via the TVMF
Biological effects of the TVMF - ANSWER -Fibrillation
,-Electroshock
-Visual phosphenes
-Peripheral nerve stimulation
SAR meaning and units - ANSWER Specific Absorption Rate
W/kg- Watts/kilogram
Which field is responsible for tissue heating and temperature increase - ANSWER The
RF field
How are cardiac pacemakers affected in MRI - ANSWER 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? - ANSWER iron, cobalt, nickel
Level 1 MR Personnel - ANSWER Passed MR safety education requirements
Level 2 MR Personnel - ANSWER Those more extensively trained and educated in MRI
safety
How many times should a non emergent patient be screened - ANSWER Twice, once
verbally with a level 2 MR Tech
How should emergent patients and their non MR personnel be screened - ANSWER
Once
, How should unconscious/ unresponsive patients be screened - ANSWER - 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 adolescents be screened?
ANSWER Twice, once in front of parents and once without
MRI and pregnant patients - ANSWER No known harmful effects but risk vs benefit
assessment should be made
MRI contrast and pregnant patients - ANSWER Should not be routinely given to pregnant
patients but risk vs benefit assessment needed
Spatial field gradient - ANSWER The fixed static field varies around the scanner, the
manufacturerer will provide a SFG map
Lenz forces - ANSWER Faradays law, a time varying magnetic field will induce a current
within a conductor, Lenzs law, the induced current within the conductor will create a
secondary field that acts in the opposite direction of the original field
TVMF (gradient) effects - ANSWER -Induced voltages
-Auditory considerations
Normal Temperature Ranges -ANSWER Adult: 36.7-37.4 C
Child (4-13): 36.7-37 C
Infant (3 mo-3 yrs.): 37.2-37.7 C
Normal Pulse Ranges -ANSWER Adult : 60-90 bpm
Child (4-10): 90-100 bpm
