Week 2 Quiz Flashcards
In a vertical field magnet, which axis corresponds to the longitudinal direction if the patient is in a head-first, supine direction?
Select one:
a. z
b. y
c. x-z
d. x
b. y
The time necessary for a proton to complete one full rotation around its precessional path is called the ____________.
Select one:
a. gyromagnetic ratio
b. precessional frequency
c. proton density
d. all of the above
b. precessional frequency
Improper tuning of the RF transmitter and/or receiver can result in:
A) Low SNR
B) Off-resonance artifact
C) Truncation
Select one:
a. A only
b. C only
c. both A & B
d. both B & C
e. all of the above
c. both A & B
Along which plane are motion artifacts seen?
Select one:
a. in the direction of the motion
b. along the frequency encoding direction of the image
c. perpendicular to the direction of motion
d. along the phase encoding direction of the image
b. along the frequency encoding direction of the image
Which physical gradient must be used for slice selection to produce a coronal image?
Select one:
a. x
b. z
c. y
c. y
A gradient echo sequence where any residual transverse magnetization is removed prior to the next excitation is called:
Select one:
a. non-residual
b. incoherent
c. coherent
d. non-phasic
b. incoherent
Which of the following parameters affects slice thickness?
Select one:
a. center frequency
b. receiver bandwidth
c. flip angle
d. transmit bandwidth
d. transmit bandwidth
Which of the following statements are FALSE?
Select one:
a. gradients can be applied to alter the phase of protons.
b. gradients are responsible for the transmission of RF energy.
c. gradients linearly vary the magnetic field.
d. gradients cause the precessional frequency of protons to vary with position.
b. gradients are responsible for the transmission of RF energy.
Magnetophosphenes are the result of stimulation of the _____________.
a. optic nerve and retina
b. olfactory nerve and cornea
c. tympanic membranes and auditory nerve
d. trigeminal nerve and lacrimal glands
a. optic nerve and retina
Decreasing the slice select gradient amplitude will have what effect on the slice (if the RF transmitter bandwidth is held constant)?
Select one:
a. increase the slice thickness
b. change the orientation of the slice
c. change the angle of the slice
d. decrease the slice thickness
a. increase the slice thickness
strength of slice select gradient decreases
= slice thickness increases
Which of the following functions is a responsibility of the RF coils?
Select one:
a. generating the magnetic field gradients
b. amplification of the MR signal
c. sampling of the MR signal
d. performing the Fourier Transform
c. sampling of the MR signal
The MRI system’s array processor is responsible for:
Select one:
a. tuning of the RF energy
b. performing Fourier transform to convert the MR signals into an image
c. selecting the sequence parameters
d. converting the signal from analog to digital format
b. performing Fourier transform to convert the MR signals into an image
The echoes emitted from the patient’s body are passed through a pre-amplifier to:
Select one:
a. digitize the echoes into a form recognizable by a computer
b. increase the strength of their signals,
c. divide the echoes into phase and frequency components
d. convert the analog echo into a digital signal
b. increase the strength of their signals
There are a total of __ carpal bones.
a. 3
b. 5
c. 7
d. 8
d. 8
The phenomenon induced in protons after exposure to a particular radiofrequency is termed:
Select one:
a. resonance
b. magnetization
c. precession
d. relaxation
a. resonance
_____________ magnets require a constant connection to a power source to maintain their magnetic field.
Select one:
a. Superconducting
b. Resistive
c. Bar
d. Permanent
b. Resistive
Which of the following statements is TRUE?
Select one:
a. permanent magnets use more cryogens than superconducting magnets
b. Cryogens should be refilled after each examination
c. Cryogen gases displace oxygen, so oxygen monitors are placed in an MR suite to alert personnel if levels become too low
d. the type of cryogenic liquids used in modern MR systems pose no danger to personnel or patients
c. Cryogen gases displace oxygen, so oxygen monitors are placed in an MR suite to alert personnel if levels become too low
The purpose of magnetic shielding is to:
Select one:
a. reduce noise levels
b. improve signal-to-noise ratio
c. contain fringe fields
d. reduce field inhomogeneity
c. contain fringe fields
Which magnetic force causes objects to rotate until they align with the magnetic field?
a. rotational force
b. translational force
c. Lenz force
d. Lorentz force
a. rotational force
Which of the following statements is FALSE regarding spatial resolution?
Select one:
a. it is affected by changes to the FOV or image matrix
b. it is calculated by dividing the matrix size by the field of view
c. it is unaffected by an increase in the number of signal averages
d. it is a measure of the smallest object that can be distinguished on the image
b. it is calculated by dividing the matrix size by the field of view
Calculate the scan time for a spin echo sequence with the following parameters:
TR = 2200ms, TE = 20, 90ms, Matrix = 256x256,
1 NEX, FOV = 230mm
Select one:
a. 9 minutes and 39 seconds
b. 10 minutes and 38 seconds
c. 5 minutes and 6 seconds
d. 8 minutes and 10 seconds
a. 9 minutes and 39 seconds
ScanTime=
TR×MatrixSize(PhaseDirection)xNEX/
1000
Which of the following is NOT related to the receiver bandwidth?
Select one:
a. chemical shift artifact
b. the readout gradient amplitude
c. the range of frequencies sampled in the echo
d. the range of frequencies transmitted to select the slice thickness
d. the range of frequencies transmitted to select the slice thickness
A ferromagnetic aneurysm clip may experience a force of _________ when the patient moves through magnetic flux lines.
Select one:
a. rotational force
b. torque
c. both A & B
d. none of the above
c. both A & B
One direction in k-space represents ______________, while the other represents ________.
Select one:
a. contrast/noise
b. intensity/signal
c. frequency/phase
d. position/contrast
c. frequency/phase
