Artifacts Flashcards
Which of the following is a form of phase mismapping?
a. phase ghosting
b. motion artifact
c. flow artifact
d. all answers are correct
d. all answers are correct
Phase mismapping only occurs along the frequency encoding axis.
true or false
false
Which of the following are not common methods of compensating for phase mismapping artifacts?
a. swap the phase and frequency encoding axes
b. decreasing concatenations
c. placing pre-saturation pulses
d. using respiratory compensation
e. decreasing the number of signals averaged
f. applying cardiac gating
g. using GMN
h. applying motion correction techniques
i. increasing the ETL
b. decreasing concatenations
e. decreasing the number of signals averaged
i. increasing the ETL
Which of the following are techniques used to reduce phase mismapping artifacts caused by respiratory motion ?
a. all answers are correct
b. respiratory gating/triggering
c. increasing NSA
d. having the patient hold his/her breath
a. all answers are correct
Which coil/FOV pairing is more sensitive to aliasing artifacts?
a. large coil w/ a small FOV
b. small coil w/ a large FOV
c. small coil w/ a small FOV
d. large coil w/ a large FOV
a. large coil w/ a small FOV
Aliasing typically occurs along the phase encoding axis.
true or false
true
Which of the following are common methods of compensating for aliasing artifacts?
a. avoid the use of oversized coils
b. increase the number of signals averaged
c. increase the ETL
d. remove all metallic objects
e. place pre-saturation pulses over unwanted anatomy
f. properly center anatomy to the RF coil
g. enlarge the phase FOV
h. applying phase oversampling
i. disengage RF coils that are not needed
a. avoid the use of oversized coils
e. place pre-saturation pulses over unwanted anatomy
f. properly center anatomy to the RF coil
g. enlarge the phase FOV
h. applying phase oversampling
i. disengage RF coils that are not needed
What imaging artifact appears as bands of high and low signal intensities running parallel to tissue interfaces?
a. truncation artifact
b. aliasing artifact
c. gibbs artifact
d. truncation or gibbs artifact
d. truncation or gibbs artifact
Truncation artifacts are commonly known to mimic _________when obtaining sagittal images of the cervical spine.
a. Chiari malformations
b. fused vertebrae
c. slipped discs
d. syrinxes
d. syrinxes
Truncation artifacts are caused by:
a. using a large FOV
b. undersampling
c. using a large phase encoding matrix
d. oversampling
b. undersampling
Truncation artifacts can be compensated for by increasing the _________ or increasing the _________.
a. NSA/NEX/ phase encoding matrix
b. # of slices / FOV
c. ETL/ phase encoding matrix
d. all answers are correct
a. NSA/NEX/ phase encoding matrix
Chemical shift artifacts occur in the phase direction.
true or false
false
The amount of chemical shift depends on which of the following?
a. magnetic field strength
b. all answers are correct
c. pixel size
d. rbw
b. all answers are correct
At 1T, the precessional frequency difference between fat and water is:
a. 256 Hz
b. 147 Hz
c. 220 Hz
d. 128 Hz
b. 147 Hz
What artifact can result from narrowing the receive bandwidth?
a. chemical shift artifact
b. magic angle artifact
c. chemical misregistration artifact
d. all answers are correct
a. chemical shift artifact
What artifact is seen here?
Susceptibility artifact
What parameter adjustments listed below can be applied in order to reduce this artifact seen on this 3D gradient echo image?
Incorporating spin echo based sequences
What artifact is seen here?
Cross-Talk
What caused the image to have this appearance?
Incorrect saturation volume placement
The artifact seen here occurs only in areas where ________ and _________ are both present within an imaging voxel.
Fat
Water
What is the cause for the artifact pictured here?
Intersecting slice groups and RF pulses
What is the artifact pictured here?
Phase aliasing / wrap
What is the artifact pictured here?
Patient Motion
The artifact pictured here occurs in which direction?
Frequency
The artifact pictured here occurs in which direction?
Phase encoding direction
What is the artifact pictured here?
Flow ghosting
A name synonymous with “chemical misregistration” artifact is:
a. Magic angle artifact
b. Out of phase artifact
c. Oversampling
d. Gibbs artifact
b. Out of phase artifact
Chemical misregistration artifact occurs more frequently during SE pulse sequences than GE pulse sequences.
True or false
False
Chemical misregistration artifacts can be compensated for _________ or _________
a. Using SE sequence/ applying a TE in intervals of 4.2 ms
b. Using SE sequence/ applying a TE in intervals of 2.1 ms
c. Using GE sequence/ applying a TE in intervals of 4.2 ms
d. Using GE sequence/ applying a TE in intervals of 2.1 ms
a. Using SE sequence/ applying a TE in intervals of 4.2 ms
Which pulse sequence decreases the effect of magnetic susceptability the greatest?
a. SE
b. All sequences have an Eco effect on magnetic susceptibility artifacts
c. FSE/TSE
d. GE
c. FSE/TSE
Radio frequency artifacts are caused by:
a. RF leaks
b. Malfunctioning ancillary equipment
c. Oversampling
d. RF leaks and malfunctioning equipment
d. RF leaks and malfunctioning equipment
What imaging artifact appears as an isolated area of an old-out signal, similar to the use of a presaturation band?
a. Susceptibility artifact
b. Crosstalk
c. Cross excitation
d. Moire pattern
b. Crosstalk
What imaging artifact appears as an overall reduction of image contrast?
a. Moire pattern
b. Cross excitation
c. Susceptibility artifact
d. Crosstalk
b. Cross excitation
Cross excitation artifacts can be compensated for:
a. Using a gap space for at least 30%/ using the interleaving imaging option
b. Using a gap space for less than 20%/ using the interleaving imaging option
c. Using a gap space for at least 30%/ using the sequential imaging option
d. Using a gap space for less than 20%/ using the sequential imaging option
a. Using a gap space for at least 30%/ using the interleaving imaging option
Moire pattern artifacts are only present gradient echo post sequences?
True or false?
True
Moire pattern artifacts are caused by:
a. Using a large fov
b. Under sampling
c. Using a large phase encoding matrix
d. Over sampling
b. Under sampling
What imaging artifact occurs when aliasing is present due to the use of multi-channel phased array coils?
a. Parallel imaging artifact
b. Moire pattern artifact
c. Magic angle artifact magic
d. Multi-channel artifact
a. Parallel imaging artifact
Parallel imaging artifacts can occur during any sequence, even when a multi-channel phased array coil and parallel imaging technique is not applied.
True or false
False
What can cause the aliasing that is evident in the presence of parallel imaging artifacts?
a. A low acceleration factor
b. A high acceleration factor
c. Proper use of a calibration scan
d. A high TR
b. A high acceleration factor
What imaging artifact appears as areas of high signal intensity near collagen dense anatomy?
a. Moire pattern artifact
b. Cross excitation artifact
c. Gibbs artifact
d. Magic angle artifact
d. Magic angle artifact
Magic angle artifact can be caused when:
a. Collagen containing structures lie at a 55° to the main magnetic field
b. Structures dense with fat are positioned at a 55° to the main magnetic field
c. Using a high TE
d. Using a high TR
a. Collagen containing structures lie at a 55° to the main magnetic field
