MRI ARMRIT UPDATED Exam Questions and CORRECT Answers
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Course
ARMRIT
Institution
ARMRIT
MRI ARMRIT UPDATED Exam
Questions and CORRECT Answers
Outside of a Large Magnetic Field: - CORRECT ANSWER- H protons orientations are
described as random.
Inside a Large Static Homogeneous Main Magnetic Field (Bo): - CORRECT ANSWERLarge Homogeneous Main Magnetic Field (Bo): Protons align bot...
MRI ARMRIT UPDATED Exam
Questions and CORRECT Answers
Outside of a Large Magnetic Field: - CORRECT ANSWER- H protons orientations are
described as random.
Inside a Large Static Homogeneous Main Magnetic Field (Bo): - CORRECT ANSWER-
Large Homogeneous Main Magnetic Field (Bo): Protons align both parallel and anti- parallel
to Bo. A small majority will align parallel. H Protons that are opposite each other cancel out
their magnetic moments and are not available as Information Units (I.U.). At this point
equilibrium has been established.
Net Magnetization: - CORRECT ANSWER- the H protons that are left over and parallel to
Bo after equilibrium has been established. The H protons that will provide information during
the MRI process.
Net Magnetization Vector: - CORRECT ANSWER- Net vector symbolized M that represents
the sum of the magnetization of all the H protons in the net magnetization.
RF Pulse: - CORRECT ANSWER- Pulse: a second smaller magnetic field in the form of
radio-frequency (RF), symbolized B1 that is introduced to the H protons in order to cause
them to move from the low energy state to the high energy state.
RF Pulse: Purpose: - CORRECT ANSWER- 1) to shift M in size and direction. 2) to cause to
H protons to precess in-phase, have phase coherence.
B1: symbolizes - CORRECT ANSWER- B1: symbolizes the RF signal that is introduced to
the patient's body in order to generate a MR signal.
Bo: - CORRECT ANSWER- Bo - a magnetic field that is constant and either horizontal or
vertical depending on the manufacturer's design.
Tesla: - CORRECT ANSWER- Tesla: Unit of magnetic flux density to describe the field
strength of the isocenter of the large, static main magnetic field symbolized Bo.
, Gauss: - CORRECT ANSWER- Gauss: Unit of magnetic flux density used to describe the
fringe field (away from isocenter) and for the much smaller gradient magnetic fields (usually
in g/cm).
Larmor Equation: - CORRECT ANSWER- Larmor Equation: Wo=BoY x Bo Solves for the
precessional frequency of the H nuclei when placed in a large external magnetic field (Bo),
where y = the gyromagnetic ratio symbolized as gamma.
Gyromagnetic Ratio: - CORRECT ANSWER- Gyromagnetic Ratio: symbolized y (gamma) A
constant for a given nuclei. It is the ratio of the magnetic moment (frequency of spin) vs. the
angular momentum of the particle. All substances have gyromagnetic ratio.
Hydrogen gyro - CORRECT ANSWER- 42.58
2DFT Scan Time Formula: - CORRECT ANSWER- TR x NEX x Matrix/ETL
3DFT Scan Time Formula: - CORRECT ANSWER- TR x NEX x #of Slices x Matrix/ETL
Fast Scan Formula: 2DFT - CORRECT ANSWER- TR x NEX x Matrix /ETL
B1 magnetic field - CORRECT ANSWER- magnetic field that is rapidly rotating (oscillating)
and always oriented perpendicular to Bo.
Signal Generation: - CORRECT ANSWER- B1 is turned off and signal decay begins and the
protons dephase.
Mz - CORRECT ANSWER- measurement of the H protons' magnetization in the longitudinal
direction.
Mxy - CORRECT ANSWER- measurement of the H protons' magnetization in the transverse
direction.
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