1
ARRT MRI exam review 2024 COMPLETE EXAM
QUESTIONS AND VERIFIED ANSWERS| 100%
ACCURATE SOLUTIONS|ALREADY GRADED A+
what is the most abundant element in the human body? - (answers)hydrogen
nuclei that are available for MRI are those that exhibit a _________ -
(answers)net spin
low energy = spin up = _______ - (answers)parallel
high energy = spin down = __________ - (answers)antiparallel
thermal equilibrium - (answers)when the body is in the magnetic field, spins are
aligned, and nothing else has happened
B0 - (answers)refers to large magnetic field of the MRI scanner
at thermal equilibrium there are a ________ portion of spins with their magnetic
moments aligned in the same direction as B0 than against it - (answers)greater
the reason why SNR increases at higher field strengths is because - (answers)the
NMV also increases in size the stronger B0
1 hertz = - (answers)1 cycle per second
larmour equation - (answers)W0 = y x B0
what do the parts of the larmor equation mean? - (answers)W0 = Larmour
frequency (precessional frequency)
, 2
y = gyromagnetic ratio (42.58 MHz/T for hydrogen)
B0 = Field strength
what is the precessional frequency for hydrogen at 1.5T? - (answers)63.87 MHz
(42.58 MHz/T x 1.5T)
out of phase or incoherent - (answers)magnetic moments of hydrogen are at
different places on the precessional path at a moment in time
in phase or coherent - (answers)magnetic moments of hydrogen are at the same
place on the precessional path at a moment in time
what two things do you need to get signal? - (answers)1) coherent
2) transverse magnetization
phase refers to - (answers)the position of a magnetic moment of a spin on its
precessional path at any moment in time
B1 field is used to deliver an RF pulse which does what 2 things -
(answers)causes 1) transverse magnetization
and 2) phase precession
an RF excitation pulse causes - (answers)resonance
transverse magnetization occurs at __ degrees to B0 - (answers)90
, 3
saturation occurs when - (answers)spins are unable to absorb more energy or to
be stimulated and release more energy
what is a saturation pulse - (answers)180 degree RF
dephasing and relaxation happen at the same time but are -
(answers)independent of eachother
relaxation - (answers)the process in which hydrogen lose energy (occurs after
RF excitation pulse is switched off)
dephasing is caused by - (answers)field inhomogeneities in the B0 field and
interactions between spins and tissue
why is it called FID (free induction decay) - (answers)spins FREEly precess
influenced only by B0, signal DECAYs with time, and magnetic moments of the
spins INDUCE a current in receiver coil
when RF excitation pulse is removed, the mag moments of all spins ____ and
______ - (answers)dephase and produce a FID
TR (repetition time) - (answers)time from application of one RF excitation
pulse to the application of the next one
determines how much longitudinal relaxation occurs (T1 weighting)
TE (echo time) - (answers)time from application of RF excitation pulse to the
peak of the signal induced in the receiver coil
determines how much decay of transverse magnetization occurs (T2 weighting)
, 4
TR controls - (answers)how much T1 relaxation occurs, recovery of
longitudinal magnetization
TE controls - (answers)how much T2 decay occurs, decaying signal of
transverse magnetization
give examples of intrinsic contrast parameters (things that cannot be changed
because they are inherent to body's tissues) - (answers)- T1 recovery time
- T2 decay time
- Proton density
- Flow
- Apparent diffusion coefficient
give examples of extrinsic contrast parameters (those that can be changed
because they are under our control) - (answers)- TR
- TE
- Flip angle
- TI
- turbo factor (ETL)
- b value
describe the process of relaxation - (answers)- B1 field is turned off
- hydrogen nuclei return to their low-energy state
- magnetic moments dephase
- NMV returns to B0
relaxation therefore results in the _______ longitudinal magnetization and the
_____ of transverse magnetization - (answers)recovery and decay
ARRT MRI exam review 2024 COMPLETE EXAM
QUESTIONS AND VERIFIED ANSWERS| 100%
ACCURATE SOLUTIONS|ALREADY GRADED A+
what is the most abundant element in the human body? - (answers)hydrogen
nuclei that are available for MRI are those that exhibit a _________ -
(answers)net spin
low energy = spin up = _______ - (answers)parallel
high energy = spin down = __________ - (answers)antiparallel
thermal equilibrium - (answers)when the body is in the magnetic field, spins are
aligned, and nothing else has happened
B0 - (answers)refers to large magnetic field of the MRI scanner
at thermal equilibrium there are a ________ portion of spins with their magnetic
moments aligned in the same direction as B0 than against it - (answers)greater
the reason why SNR increases at higher field strengths is because - (answers)the
NMV also increases in size the stronger B0
1 hertz = - (answers)1 cycle per second
larmour equation - (answers)W0 = y x B0
what do the parts of the larmor equation mean? - (answers)W0 = Larmour
frequency (precessional frequency)
, 2
y = gyromagnetic ratio (42.58 MHz/T for hydrogen)
B0 = Field strength
what is the precessional frequency for hydrogen at 1.5T? - (answers)63.87 MHz
(42.58 MHz/T x 1.5T)
out of phase or incoherent - (answers)magnetic moments of hydrogen are at
different places on the precessional path at a moment in time
in phase or coherent - (answers)magnetic moments of hydrogen are at the same
place on the precessional path at a moment in time
what two things do you need to get signal? - (answers)1) coherent
2) transverse magnetization
phase refers to - (answers)the position of a magnetic moment of a spin on its
precessional path at any moment in time
B1 field is used to deliver an RF pulse which does what 2 things -
(answers)causes 1) transverse magnetization
and 2) phase precession
an RF excitation pulse causes - (answers)resonance
transverse magnetization occurs at __ degrees to B0 - (answers)90
, 3
saturation occurs when - (answers)spins are unable to absorb more energy or to
be stimulated and release more energy
what is a saturation pulse - (answers)180 degree RF
dephasing and relaxation happen at the same time but are -
(answers)independent of eachother
relaxation - (answers)the process in which hydrogen lose energy (occurs after
RF excitation pulse is switched off)
dephasing is caused by - (answers)field inhomogeneities in the B0 field and
interactions between spins and tissue
why is it called FID (free induction decay) - (answers)spins FREEly precess
influenced only by B0, signal DECAYs with time, and magnetic moments of the
spins INDUCE a current in receiver coil
when RF excitation pulse is removed, the mag moments of all spins ____ and
______ - (answers)dephase and produce a FID
TR (repetition time) - (answers)time from application of one RF excitation
pulse to the application of the next one
determines how much longitudinal relaxation occurs (T1 weighting)
TE (echo time) - (answers)time from application of RF excitation pulse to the
peak of the signal induced in the receiver coil
determines how much decay of transverse magnetization occurs (T2 weighting)
, 4
TR controls - (answers)how much T1 relaxation occurs, recovery of
longitudinal magnetization
TE controls - (answers)how much T2 decay occurs, decaying signal of
transverse magnetization
give examples of intrinsic contrast parameters (things that cannot be changed
because they are inherent to body's tissues) - (answers)- T1 recovery time
- T2 decay time
- Proton density
- Flow
- Apparent diffusion coefficient
give examples of extrinsic contrast parameters (those that can be changed
because they are under our control) - (answers)- TR
- TE
- Flip angle
- TI
- turbo factor (ETL)
- b value
describe the process of relaxation - (answers)- B1 field is turned off
- hydrogen nuclei return to their low-energy state
- magnetic moments dephase
- NMV returns to B0
relaxation therefore results in the _______ longitudinal magnetization and the
_____ of transverse magnetization - (answers)recovery and decay
