Study Guide for MRI CAMRT Exam Questions and Answers Latest Updated
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Course
MRI CAMRT
Institution
MRI CAMRT
Study Guide for MRI CAMRT Exam
Questions and Answers Latest Updated
Is SNR proportional or inversely proportional to voxel volume - CORRECT ANSWERProportional
3 fields used in MRI - CORRECT ANSWER--static magnetic field
-TVMF (gradient field)
-RF field
3 main types of magnets used - CORRECT...
Study Guide for MRI CAMRT Exam
Questions and Answers Latest Updated
Is SNR proportional or inversely proportional to voxel volume - CORRECT ANSWER-
Proportional
3 fields used in MRI - CORRECT ANSWER--static magnetic field
-TVMF (gradient field)
-RF field
3 main types of magnets used - CORRECT ANSWER--Superconducting (most
common_
-Resistive
-Permanent
FDA limits for the 3 fields in MRI - CORRECT 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 - CORRECT ANSWER-TVMF (gradients)
What are Eddy Currents - CORRECT ANSWER-Small currents induced in the body via
the TVMF
Biological effects of the TVMF - CORRECT ANSWER--Fibrillation
-Electroshock
-Visual phosphenes
-Peripheral nerve stimulation
SAR meaning and units - CORRECT ANSWER-Specific Absorption Rate
W/kg- Watts/kilogram
Which field is responsible for tissue heating and temperature increase - CORRECT
ANSWER-The RF field
How are cardiac pacemakers affected in MRI - CORRECT 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? - CORRECT ANSWER-iron, cobalt, nickel
Level 2 MR Personnel - CORRECT ANSWER-Those more extensively trained and
educated in MRI safety
How many times should a non emergent patient be screened - CORRECT ANSWER-
Twice, once verbally with a level 2 MR Tech
How should emergent patients and their non MR personnel be screened - CORRECT
ANSWER-Once
How should unconscious/ unresponsive patients be screened - CORRECT 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 - CORRECT ANSWER-Twice, once in front
of parents and once without
MRI and pregnant patients - CORRECT ANSWER-No known harmful effects but risk vs
benefit assessment should be made
MRI contrast and pregnant patients - CORRECT ANSWER-Should not be routinely
given to pregnant patients but risk vs benefit assessment needed
What is the spatial field gradient - CORRECT ANSWER-The variance in the fixed static
field surrounding the scanner, the manufacturerer supplies a SFG map
Lenz forces - CORRECT 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
Normal respiratory ranges - CORRECT ANSWER-Adult: 15-20 breaths per minute
Infant: 30-60 breaths per minute
Normal pulse oximetry - CORRECT ANSWER-95%-100%
Tachycardia - CORRECT ANSWER-Fast heart rate over 100 bpm
Bradycardia - CORRECT ANSWER-Slow heart rate less than 60 bpm
Spots to get a pulse reading - CORRECT ANSWER--Radial (wrist)
-Carotid (neck)
-Popliteal (knee)
-Temporal (head)
-Brachial (elbow)
-Dorsalis pedis (foot)
-Femoral(leg)
Most accurate spot for pulse rate in infants - CORRECT ANSWER-Apical over apex of
the heart
Normal BP ranges - CORRECT ANSWER-Adult: 80-120mmHg/60-80mmHg
Child: 90-120mmHg/50-70mmHg
Infant: 85-130mmHg/45-85mmHg
3 types of motion in an atom - CORRECT ANSWER-(1) Electron on its axis (2) Electron
around the nucleus (3) Nucleus on its axis
Isotope of hydrogen - CORRECT ANSWER-protium (MR active nuclei)
True or false: Hydrogen nuclei only align themselves to the field in 2 directions -
CORRECT ANSWER-True
As Bo increases what happens to the difference in energy between high and low energy
states - CORRECT ANSWER-increases - more spins aligned to Bo means larger NMV
which means more signal
Larmour frequency - CORRECT ANSWER-The precessional or resonant frequency
(w0) of a nuclear spin when it is placed in an external magnetic field.
It is related to the magnetic field (Bₒ) by the Larmor equation:
Wₒ=ϒ * B ₒ
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