Artifacts

Question 1

Result of averaging the linear attenuation coefficent in a vocxel that is heterogeneous in composition

Answer 1

Partial Volume

Question 2

Results in star and streak artifacts along rays through high density structures

Answer 2

Photon starvation

Question 3

Help minimize streak artifacts

Answer 3

Iterative reconstruction

Question 4

Caused by lower-energy photons being preferentially absobed, resulting in a more penetrating(high-energy) beam

Answer 4

Beam artifacts

Question 5

When edges are imaged because of inadequate data sampling

Answer 5

Aliasing Artifacts

Question 6

Occur with large detectors due to inadequate anatomical coverage related to under sampling in the cone beam direction

Answer 6

Cone beam artifacts

Question 7

Caused by slight difference in resonance frequency of protons in water and in fat, resulting in miregistration and water

Answer 7

Chemical shift artifact

Question 8

Patterns of dark and birght bands adjacent to a sharp edge, which is minimized by increasing the matrix size

Answer 8

Truncation artifacts

Question 9

Truncation artifacts which may simulate a syrinx in a spinal cord

Answer 9

Gibbs/Ringing

Question 10

When the FOV is smaller than the structure, and imaged objects outsid the FOV are mapped to the opposite side of the image

Answer 10

Wrap-around artifact

Question 11

Wrap around artifact is caused by

Answer 11

Under sampling (aliasing)

Question 12

Under sampling (aliasing) can be reduced by

Answer 12

Increasing FOV

Question 13

Flowing blood and CSF can result in MR image artifacts, which occur along

Answer 13

Phase encoding direction

Question 14

Maging angle artifacts disappear on?

Answer 14

T2WI

Question 15

Occur where sound is reflected off of a large interface such as diaphragm causing parts of teh image to be in the wrong location

Answer 15

Mirror images

Question 16

Caused by variability of the speed of sound in different tissues

Answer 16

Speed displacement artifacts

Question 17

Multiple reflections occuring from to adjacent interface

Answer 17

Reverberation echoes

Question 18

Oberved when the gap between reverberation echoes becomes very small,

Answer 18

Comet artifacts

Question 19

Streak like appearance from mixtures of gas and fluids

Answer 19

Ring-down artifacts

Question 20

Reduced echo intensity behind a hight attenuating or reflective object such as a stone creating a shadow

Answer 20

Acoustic shadowing

Question 21

Increased echo intensity behind a minimally attenuating object such as a cyst or blood vessel

Answer 21

Acoustic enhancement