MRI Artifacts: Susceptibility and Zipper Artifacts
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Questions and Answers

What is the primary cause of zipper artifacts in MRI images?

  • Weak signal coming from the patient
  • External RF entering the scanning room (correct)
  • Leaking RF signals from the machine
  • Hardware or software problems

    • What is the orientation of zipper artifacts caused by RF from radio transmitters?

  • Parallel to the frequency axis of the image
  • At an angle to the frequency axis of the image
  • Perpendicular to the frequency axis of the image (correct)
  • Randomly oriented

    • What should be done with system-generated artifacts?

  • Report them to the radiologist
  • Ignore them
  • Try to fix them manually
  • Report them to the service engineer (correct)

    • What can cause streak artifacts in MRI images?

    <p>Leaking RF signals</p> Signup and view all the answers

    What type of artifact is caused by external RF entering the scanning room?

    <p>Zipper artifact</p> Signup and view all the answers

    What is the optimal combination for cervical and thoracic imaging?

    <p>Combination of 'Gating' and flow compensation</p> Signup and view all the answers

    What is the cause of the point artifact in MRI images?

    <p>Constant offset of DC voltage in the receiver coil</p> Signup and view all the answers

    What is the result of slices not being parallel in multiangle, multislice acquisitions in the lumbar spine?

    <p>A band of signal loss crossing horizontally or vertically in the image</p> Signup and view all the answers

    What is the term used to describe the ability of a tissue to be magnetized?

    <p>Susceptibility</p> Signup and view all the answers

    Where are tissue-air interphases related artifacts commonly seen?

    <p>Around the paranasal sinuses and the lungs</p> Signup and view all the answers

    What is the result of the presence of paramagnetic material like hemoglobin degradation products in MRI images?

    <p>Reduction in the quality of the local field</p> Signup and view all the answers

    What is the primary cause of chemical shift artifacts?

    <p>Different precessional frequencies of protons in water and fat</p> Signup and view all the answers

    What is the result of the phase of the signal just outside of the field of view?

    <p>Wrap around artifact</p> Signup and view all the answers

    What type of artifact occurs when the diameter of the scanned area is greater than the dimensions of the field of view used?

    <p>Wrap around or aliasing artifact</p> Signup and view all the answers

    What is the primary method to rectify artifacts?

    <p>Identifying and understanding the causes of artifacts</p> Signup and view all the answers

    What type of artifact can simulate pathology that does not exist?

    <p>Any type of artifact</p> Signup and view all the answers

    What type of artifact is related to the random fluctuation of intensity due to noise?

    <p>Noise artifact</p> Signup and view all the answers

    Study Notes

    MRI Artifacts

    • Combination of 'Gating' and flow compensation is optimal for cervical and thoracic imaging.

    Point Artifact

    • Appears as a bright spot of increased signal intensity in the center of the image.
    • Caused by constant offset of DC voltage in the receiver coil.

    Slice Overlap Artifact

    • Characterized by loss of signal in an image from multiangle, multislice acquisitions.
    • Occurs when slices obtained at different disk spaces are not parallel.
    • Causes a band of signal loss crossing horizontally or vertically in the image, usually prominent posteriorly.

    Susceptibility Artifacts

    • Caused by local variations in susceptibility due to presence of paramagnetic material like hemoglobin degradation products or tissue-air interphases.
    • Results in reduction in the quality of the local field.
    • Tissue air interphases related artifacts are commonly seen around the paranasal sinuses and the lungs.
    • Can be removed by using spin echo sequences.

    Zipper Artifacts

    • Caused by external RF entering the room at a certain frequency and interfering with the inherently weak signal coming from the patient.
    • Can be caused by RF entering the scanning room when the door is open during acquisition of images.
    • RF from radio transmitters will cause zipper artifacts that are oriented perpendicular to the frequency axis of the image.

    Classification of Artifacts

    • Artifacts can be classified into different categories, including:
      • Aliasing
      • Chemical shift
      • Gibbs/truncation
      • Magic angle
      • Motion
      • Point
      • Slice overlap
      • Susceptibility
      • Zipper
      • Array processing
      • Col selection
      • Wrap Around/Aliasing

    Wrap Around/Aliasing Artifact

    • Appears when the diameter of the scanned area is greater than the dimensions of the field of view used.
    • A part of the image is folded on itself.
    • Remedies include:
      • Increasing FOV
      • Filtering the frequency encoded direction
      • Oversampling in the phase encoded direction

    Chemical Shift Artifacts

    • Appear at the interfaces between water and fat because the precessional frequency of protons is slightly different in these two substances.
    • Lead to misregistration of the signals.

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    Quiz Team

    Description

    This quiz covers the causes and removal of susceptibility artifacts in MRI images, as well as zipper artifacts caused by external RF interference and hardware/software problems.

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