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
