MRI CAMRT Exam Study Guide Questions and Answers Top Graded 2024
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Course
MRI CAMRT
Institution
MRI CAMRT
Is SNR proportional or inversely proportional to voxel volume - ANSWERS-Proportional
3 fields used in MRI - ANSWERS--static magnetic field
-TVMF (gradient field)
-RF field
3 main types of magnets used - ANSWERS--Superconducting (most common_
-Resistive
-Permanent
FDA limits for the 3 f...
MRI CAMRT Exam Study Guide Questions and
Answers Top Graded 2024
Is SNR proportional or inversely proportional to voxel volume - ANSWERS-Proportional
3 fields used in MRI - ANSWERS--static magnetic field
-TVMF (gradient field)
-RF field
3 main types of magnets used - ANSWERS--Superconducting (most common_
-Resistive
-Permanent
FDA limits for the 3 fields in MRI - ANSWERS-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 - ANSWERS-TVMF (gradients)
What are Eddy Currents - ANSWERS-Small currents induced in the body via the TVMF
Biological effects of the TVMF - ANSWERS--Fibrillation
-Electroshock
-Visual phosphenes
-Peripheral nerve stimulation
SAR meaning and units - ANSWERS-Specific Absorption Rate
W/kg- Watts/kilogram
Which field is responsible for tissue heating and temperature increase - ANSWERS-The
RF field
How are cardiac pacemakers affected in MRI - ANSWERS-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? - ANSWERS-iron, cobalt, nickel
Level 2 MR Personnel - ANSWERS-Those more extensively trained and educated in
MRI safety
How many times should a non emergent patient be screened - ANSWERS-Twice, once
verbally with a level 2 MR Tech
How should emergent patients and their non MR personnel be screened - ANSWERS-
Once
How should unconscious/ unresponsive patients be screened - ANSWERS-- 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 - ANSWERS-Twice, once in front of
parents and once without
MRI and pregnant patients - ANSWERS-No known harmful effects but risk vs benefit
assessment should be made
MRI contrast and pregnant patients - ANSWERS-Should not be routinely given to
pregnant patients but risk vs benefit assessment needed
What is the spatial field gradient - ANSWERS-The variance in the fixed static field
surrounding the scanner, the manufacturerer supplies a SFG map
Lenz forces - ANSWERS-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
Normal respiratory ranges - ANSWERS-Adult: 15-20 breaths per minute
Infant: 30-60 breaths per minute
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