Gamma Camera Uniformity Test
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Questions and Answers

What is the purpose of a flood field or sheet phantom in a gamma camera?

  • To analyze the performance of individual photomultipliers
  • To measure the level of background radiation
  • To detect contamination of the gamma camera
  • To check the uniformity of the detector response (correct)
  • What is the advantage of using 57Co in a flood field or sheet phantom?

  • It is less expensive than 99mTc
  • It has a shorter half-life than 99mTc
  • It has a similar gamma emission to 99mTc but is longer-lived (correct)
  • It is more easily available than 99mTc
  • What does a defective photomultiplier tube appear as in a flood field image?

  • A linear defect
  • A circular defect
  • An area of increased counts
  • An area of reduced counts (correct)
  • What is the purpose of regular checks on the photomultipliers?

    <p>To monitor any deterioration in the photomultipliers</p> Signup and view all the answers

    What does a high reading obtained with the collimator in place indicate?

    <p>Contamination on the crystal or the camera head</p> Signup and view all the answers

    What can cause a linear defect in a flood field image?

    <p>A cracked crystal</p> Signup and view all the answers

    Study Notes

    Uniformity of Detector Response

    • A conventional gamma camera is expected to provide a uniform response to a uniform field, which is checked using a flood field or sheet phantom.
    • A flood field consists of a flat, sealed plate larger than the field of view (FOV), typically filled with cobalt-57 (57Co).
    • Cobalt-57 has a similar gamma emission to technetium-99m (99mTc) but has a longer half-life.
    • The flood field test should produce a uniform image with the collimator in place, allowing identification of defective photomultipliers as areas of reduced counts.
    • Crystal defects, such as cracks, appear as linear defects in the image.
    • Non-uniformity due to minor differences in photomultiplier performance is analyzed by counting pixels, and image data can be automatically compensated based on this analysis.
    • Regular checks are necessary to monitor photomultiplier deterioration over time.

    Background Radiation Checks

    • Background radiation checks help identify contamination on the gamma camera or collimator, or the presence of a local unshielded source.
    • High readings, regardless of camera orientation, indicate contamination on the crystal or camera head.
    • Subsequent high readings, obtained with the collimator in place, suggest collimator contamination.

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    Description

    Learn about the uniformity test of a conventional gamma camera using a flood field or sheet phantom. Understand how it's used to check the camera's response and detect defects.

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