MRI MRI Artifacts 1

Question 1

Which MRI artifact appears as a ghosting or smearing of bright structures in the phase-encoding direction?

Accepted Answer

Motion (ghosting) artifact

Answer

Chemical shift artifact

Answer

Gibbs (truncation) artifact

Answer

Susceptibility artifact

Question 2

Chemical shift artifact of the first kind occurs at interfaces between fat and water and manifests as:

Accepted Answer

A bright band and a dark band at the fat-water interface in the frequency-encoding direction

Answer

Signal voids around metallic implants

Answer

Zebra-stripe banding artifact

Answer

Image wrap-around from the opposite side

Question 3

Gibbs (truncation) artifact is caused by:

Accepted Answer

Undersampling of k-space — insufficient high-frequency data to represent sharp tissue interfaces

Answer

Patient motion during scanning

Answer

Field inhomogeneity near air-tissue interfaces

Answer

Aliasing from a FOV smaller than the patient

Question 4

Wraparound (aliasing) artifact in MRI is caused by:

Accepted Answer

Structures outside the FOV contributing signal that is folded back into the image

Answer

Gradient non-linearity at the edges of the bore

Answer

T2* dephasing from metallic objects

Answer

Phase errors from pulsatile flow

Question 5

Which technique is most effective for reducing susceptibility artifact from a metallic implant in MRI?

Accepted Answer

Use a spin-echo or fast spin-echo (FSE) sequence with narrow bandwidth

Answer

Increase TE

Answer

Use a gradient-echo sequence

Answer

Increase the slice thickness

Question 6

Zipper artifact on an MRI image appears as a line of alternating bright and dark pixels across the image, most often caused by:

Accepted Answer

External RF interference from inadequate shielding or open RF cage door

Answer

Patient movement

Answer

Gradient switching noise

Answer

Coil coupling artifact