Artifacts

Question 1

the superimposition of a signal that occurs when a LRGE FOV is acquired is known as

Answer 1

partial volume averaging

Question 2

the superimposition that occurs when a SMALL FOV is used known as

Answer 2

wrap around

fold over

aliasing

Question 3

motion is seen as a smearing in the

Answer 3

phase encoding direction

Question 4

aliasing occurs because tissue outsied the selcted FOV is

Answer 4

undersampled

Question 5

in order to compensate for aliasing

Answer 5

the FOV can be changed

an oversampling technique can be employed

Question 6

GIbbs or truncation artifact is seen as

Answer 6

high and low signal intensity bands

Question 7

chemical shift occurs because the

Answer 7

fat and water precess at different frequencies

Question 8

chemical shift is more obvious as the

Answer 8

receiver bandwidth is decreases

Question 9

magnetic susceptibility effects are more prominent with

Answer 9

gradient echo sequences

Question 10

magnetic susceptibility effects can be reduced by

Answer 10

reducing FOV

reducing the TE

Question 11

a leak in the RF shielding can appear as a

Answer 11

zipper artifact int he frequency direction

Question 12

flow artifacts can be reduced by

Answer 12

gradient moment nulling

spatial presaturation pulses

shortening the TE

Question 13

a decrease in voxel volume leads to a decrease in

Answer 13

chemical shift

partial volume averaging

Question 14

as FOV increases partial volume averaging

Answer 14

increases

Question 15

as slice thickness increases partial volume averaging

Answer 15

increases

Question 16

a matrix increases partial volume averages

Answer 16

decreases

Question 17

as TR increases partial volume averaging

Answer 17

is not affected

Question 18

respiratory artifacts can be reduced by

Answer 18

respiratory gating

respiratoy triggering

increasing the number of signals averaged

Question 19

motion artifact occurs due to period and or aperiodic motion whereby respiraoty motion is an example of

Answer 19

periodic

Question 20

motion artifact occurs due to periodic and or aperiodic motion whereby cardia motin is an example of

Answer 20

periodic motion

Question 21

motion artifact occurs due to periodic and or aperiodic motion whereby patient movement is an example of

Answer 21

aperiodic motion

Question 22

motion artifact occurs due to periodic and or aperiodic motion whereby peristaltic motion is an example of

Answer 22

aperiodic