CAMRT EXAM ACTUAL EXAM 300 QUESTIONS AND
CORRECT DETAILED ANSWERS WITH RATIONALES
(VERIFIED ANSWERS) |AGRADE
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 are 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 teens 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
What is the spatial field gradient - ANSWER: The variance in the fixed static field
surrounding the scanner, the manufacturerer supplies a SFG map
Lenz forces - ANSWER: 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 - ANSWER: -Induced voltages
-Auditory considerations
Normal temperature ranges - ANSWER: Adult: 36.7-37.4 C
Child (4-13): 36.7-37 C
Infant (3mo-3yrs): 37.2-37.7 C
Normal pulse ranges - ANSWER: Adult: 60-90 bpm
Child (4-10): 90-100 bpm
Infant: 120 bpm
Normal respiratory ranges - ANSWER: Adult: 15-20 breaths per minute
Infant: 30-60 breaths per minute
CORRECT DETAILED ANSWERS WITH RATIONALES
(VERIFIED ANSWERS) |AGRADE
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 are 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 teens 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
What is the spatial field gradient - ANSWER: The variance in the fixed static field
surrounding the scanner, the manufacturerer supplies a SFG map
Lenz forces - ANSWER: 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 - ANSWER: -Induced voltages
-Auditory considerations
Normal temperature ranges - ANSWER: Adult: 36.7-37.4 C
Child (4-13): 36.7-37 C
Infant (3mo-3yrs): 37.2-37.7 C
Normal pulse ranges - ANSWER: Adult: 60-90 bpm
Child (4-10): 90-100 bpm
Infant: 120 bpm
Normal respiratory ranges - ANSWER: Adult: 15-20 breaths per minute
Infant: 30-60 breaths per minute
