Understanding Aliasing Artifact in Medical Imaging
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Questions and Answers

Which artifact occurs when anatomy outside the FOV is folded onto the top of anatomy inside the FOV?

  • Appearance Aliasing (correct)
  • Signal distortion
  • Frequency wrap
  • Phase wrap

    • What causes appearance aliasing?

  • Undersampling of data
  • Frequency encoding
  • Signal distortion
  • Gradients (correct)

    • What is the term for aliasing along the frequency encoding axis?

  • Signal distortion
  • Frequency wrap (correct)
  • Appearance Aliasing
  • Phase wrap

    • What happens when the FOV is smaller than the anatomy in the frequency direction of the image?

    <p>Frequencies outside the FOV are represented as a lower frequency (D)</p> Signup and view all the answers

    What is the term for aliasing along the phase axis of the image?

    <p>Phase wrap (C)</p> Signup and view all the answers

    What causes phase wrap?

    <p>Undersampling of data (A)</p> Signup and view all the answers

    What happens when the FOV in the phase encoding axis is smaller than the dimensions of the abdomen?

    <p>Phase wrap occurs (C)</p> Signup and view all the answers

    What frequencies are accurately digitized in the FOV?

    <p>All frequencies within the FOV (C)</p> Signup and view all the answers

    What happens to frequencies outside the FOV that exceed the Nyquist frequency?

    <p>They are represented as a lower frequency (A)</p> Signup and view all the answers

    What is the term for the artifact where anatomy outside the FOV is folded onto the top of anatomy inside the FOV?

    <p>Appearance Aliasing (D)</p> Signup and view all the answers

    Which technique is used to eliminate aliasing in the frequency direction?

    <p>Increasing the digital sampling rate (A)</p> Signup and view all the answers

    What is the purpose of using presaturation bands?

    <p>To null signal from areas outside the FOV (D)</p> Signup and view all the answers

    What is the term used to describe antialiasing along the phase axis?

    <p>No phase wrap (A)</p> Signup and view all the answers

    How does increasing the number of phase encodings steps compensate for aliasing along the phase axis?

    <p>By increasing the number of k-space lines (D)</p> Signup and view all the answers

    What can happen if the volume imaging does not include all of the anatomy lying outside the region under investigation?

    <p>Aliasing will occur in the slice-select direction (A)</p> Signup and view all the answers

    How is aliasing in the frequency direction eliminated?

    <p>Increasing the digital sampling rate (A)</p> Signup and view all the answers

    What is the effect of enlarging the FOV to compensate for aliasing along the phase axis?

    <p>It increases the scan time (D)</p> Signup and view all the answers

    What is the purpose of antialiasing software methods?

    <p>To reduce aliasing along the phase axis (C)</p> Signup and view all the answers

    What is the term used to describe aliasing along both the frequency and phase axes?

    <p>Remedy Aliasing (B)</p> Signup and view all the answers

    What happens when aliasing occurs in the slice-select direction in volume imaging?

    <p>Undersampling during the process (A)</p> Signup and view all the answers

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