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MRI Artifacts Flashcards

6 cards from real MRI practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 6 MRI Artifacts flashcards as text

  1. Pulsatile flow artifact from a vessel typically appears as ghost images displaced in which direction?

    Answer: Phase-encoding direction

    Pulsatile flow ghosts appear in the phase-encoding direction because pulsatile variations in spin phase occur between TR intervals during phase-encode data collection.

  2. Which of the following best describes the 'magic angle' artifact and at what angle it occurs?

    Answer: Artifactual T1/PD signal increase in ordered collagen structures at ~55° to B0

    When ordered collagen fibers (tendons, ligaments) are oriented at ~55° to B0, dipole-dipole interactions average to zero, artifactually increasing signal on short TE sequences.

  3. A 'DC offset' or 'center dot' artifact seen as a bright spot in the center of the image is related to:

    Answer: A small DC current offset in the receiver causing a spike in the center of k-space

    A DC offset artifact occurs when a constant voltage offset in the MR receiver chain introduces a spike at the origin of k-space (DC component), appearing as a bright dot at image center.

  4. EPI (echo planar imaging) sequences are particularly prone to which artifact caused by off-resonance spins accumulating phase during the long readout?

    Answer: Chemical shift (N/2 ghost or Nyquist ghost) and geometric distortion

    EPI's long readout makes it sensitive to field inhomogeneity, causing geometric distortion along the phase-encode direction and N/2 ghosting from alternating echo phase inconsistencies.

  5. Which artifact appears as parallel bright and dark bands in the phase-encoding direction when the FOV is too small and the patient extends beyond it?

    Answer: Aliasing (wraparound)

    When anatomy outside the FOV is phase-encoded, it aliases (wraps around) and appears as a superimposed copy on the opposite edge of the image, sometimes appearing as bands.

  6. Cross-excitation (cross-talk) artifact in multislice MRI occurs because of:

    Answer: Imperfect slice profiles causing RF excitation of adjacent slices

    Real RF pulses have imperfect rectangular profiles; the tails of adjacent slice profiles overlap, causing partial saturation of neighboring slices — reduced by interleaved acquisition or adding gaps.