MRI IN PRACTICE FINAL EXAM ACCOMPANEID WITH VERIFIED QUESTIONS & ANSWERS..
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MRI IN PRACTICE FINAL EXAM
ACCOMPANEID WITH VERIFIED QUESTIONS
& ANSWERS..
Resonance - CORRECT ANSWER --A phenomenon that occurs when two objects
naturally vibrate at the same frequency.
Results of resonance - CORRECT ANSWER --The direction of the NVM shifts as
they transition to high ener...
mri in practice final exam accompaneid with verifi
resonance correct answer a phenomenon that occ
results of resonance correct answer the direct
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MRI IN PRACTICE FINAL EXAM
ACCOMPANEID WITH VERIFIED QUESTIONS
& ANSWERS..
Resonance - CORRECT ANSWER --A phenomenon that occurs when two objects
naturally vibrate at the same frequency.
Results of resonance - CORRECT ANSWER --The direction of the NVM shifts as
they transition to high energy. Away from Bo
The angle to which the NMV moves out of alignment with the Bo is called FLIP
ANGLE
Effect of RF Pulse - CORRECT ANSWER --1)hydrogen protons absorbs the RF
energy
2)increases the # of spin down hydrogen nuclei
SPIN UP NUCLEI GAIN ENERGY THROUGH RESONANCE
Flip angle - CORRECT ANSWER --the angle to which the longitudinal magnetization
is tipped into the transverse plane, following the initial RF excitation pulse
Faraday's Law - CORRECT ANSWER --When a conductive receiver coil is placed in
the area of a moving magnetic field, a voltage is induced in it.
Resonance causes protons to precession in phase in the transverse plane, this
generates an electric current.
The MR signal is produced when when in-phase magnetization cuts across the coil.
Magnitude of MR signal - CORRECT ANSWER --Depends on the amount of
magnetization present in the transverse plane
-Small magnetization transverse plane=LOW SIGNAL {Hypo-intense, DARK}
-Large magnetization=HIGH SIGNAL {hyper-intense, BRIGHT}
relaxation - CORRECT ANSWER --The process by which hydrogen transition back
to low energy state.
When the RF pulse is removed the NMV, the NMV is influenced by Bo:
1.The protons move out of phase (dephase) with each other causing the transverse
magnetization to slowly disappear.
2.Protons return to lower energy level (relax) to the resting state of net longitudinal
magnetization (Mz)
Free Induction Decay Signal (FID) - CORRECT ANSWER --The loss of
signal/voltage
As the transverse magnetization decreases, so does the magnitude induced in the
receiver coil.
This occurs by the inhomogeneities, causing the protons to lose coherency
(deodars)
pulse sequence - CORRECT ANSWER --a series of RF pulses, gradient applications
and intervening time periods
, Dramatically impacts the appearance of a MRI image
MRI obtain various contrast images using pulse sequence.
All help to visualize different anatomy and pathology
pulse timing parameters - CORRECT ANSWER --a. A sequence of transmitting rf
pulses during precise times with interviening periods of recovery.
Repetition Time (TR)
Echo Time (TE)
Echo Time (TE) - CORRECT ANSWER --Time in milliseconds from the application of
the RF pulse to the peak of the signal induced in the coil. TE determines how much
decay of transverse magnetization is allowed to occur
Intrinsic Contrast Parameters - CORRECT ANSWER --those parameters that cannot
be changed because they are inherent to the body's tissues
T1 recovery time
T2 Decay Time
Proton density
Flow
Apparent diffusion coefficient (ADC)
Extrinsic Contrast Parameters - CORRECT ANSWER --those parameters that can
be changed at the operator console
Repetition time (TR)
Echo time (TE)
Flip angle
Inversion Time (TI)
Turbo factor or echo train Length (ETL)
T1 RECOVERY (SPIN LATTICE RELAXATION) - CORRECT ANSWER --Recovery
of longitudinal magnetization
(Gradually INCREASES).
Time it takes the protons to recover 63% of its longitudinal magnetization
Involves the nuclei giving up their energy to the surrounding environment
Occurs at different rates in different tissues
Repetition Time (TR) - CORRECT ANSWER --time between each excitation pulse
T2 Decay (Spin spin relaxation) - CORRECT ANSWER --loss of transverse
magnetization as a result of spin-spin relaxation
Interactions between neighboring nuclei cause dephasing (energy loss)
Involves loss of phase coherence
T2 Decay Time - CORRECT ANSWER --The time it takes 63% of the transverse
magnetization to dephase (37% in-phase) in a tissue.
The rate of decay is also an exponential process & occurs in different tissues.
T2* Decay - CORRECT ANSWER --Caused by the immediate deplaning of spins in
the transverse Mxy plane once the RF pulse is turned off.
Detected by receiver coil immediately after the termination of the RF pulse.
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