CT Imaging and MRI Quiz
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Questions and Answers

What is the primary purpose of the filter in an x-ray tube used in CT imaging?

  • To limit the x-ray beam
  • To generate Bremsstrahlung x-rays
  • To shape the x-ray beam (correct)
  • To remove low-energy x-rays from the beam

    • What type of image looks very different from non-attenuation corrected images in PET?

  • Dead-time corrected image
  • Attenuation corrected image (correct)
  • Partial volume effect-corrected image
  • Scatter-corrected image

    • What are the approximate CT number ranges for air, soft tissue, and bone?

  • Air: -500, Soft tissue: -150 - +150, Bone: +200 - +800
  • Air: -1000, Soft tissue: -200 - +200, Bone: +300 - +1000 (correct)
  • Air: -800, Soft tissue: -250 - +250, Bone: +350 - +900
  • Air: -1500, Soft tissue: -300 - +300, Bone: +400 - +1200

    • What is the biggest contributor to dead time in PET/CT imaging?

    <p>Single events</p> Signup and view all the answers

    What does pitch change the amount of radiation a patient is exposed to in CT imaging?

    <p>Higher pitch decreases radiation exposure</p> Signup and view all the answers

    What uses a 2D projection to make a 3D image in nuclear medicine imaging?

    <p>&quot;Iterative Reconstruction&quot;</p> Signup and view all the answers

    What is the purpose of detecting annihilation photons in coincidence imaging?

    <p>To determine the location of annihilation</p> Signup and view all the answers

    What happens to the annihilation photons if they are not determined to be in coincidence during a PET scan?

    <p>They are discarded</p> Signup and view all the answers

    Which radionuclide is NOT cyclotron produced and is used for Myocardial perfusion imaging?

    <p>Rb-82</p> Signup and view all the answers

    What is the energy of the annihilation photons emitted from positron-emitting radionuclides?

    <p>511 keV</p> Signup and view all the answers

    What is the role of the Pulse Height Analyzer in coincidence imaging?

    <p>Detecting the annihilation photons</p> Signup and view all the answers

    Why is it necessary for the annihilation photons to be detected by both detectors on each side during coincidence imaging?

    <p>To ensure accurate localization of annihilation events</p> Signup and view all the answers

    What component is used in 2D PET imaging to absorb cross plane annihilation photons and improve image quality?

    <p>Tungsten septa</p> Signup and view all the answers

    In PET imaging, what is the purpose of time of flight (TOF) technology?

    <p>To measure the time difference between the detection of two gamma rays</p> Signup and view all the answers

    What is the main advantage of MRI over CT in terms of imaging?

    <p>Suitable for soft tissue imaging</p> Signup and view all the answers

    What type of x-rays are selectively removed by the filter in an x-ray tube used in CT imaging?

    <p>'Soft' x-rays</p> Signup and view all the answers

    What does pitch change the amount of radiation a patient is exposed to in CT imaging?

    <p>Higher pitch decreases radiation exposure</p> Signup and view all the answers

    What refers to the ability of an imaging system to detect and accurately measure the gamma rays emitted by radioactive tracers administered to a patient?

    <p>System sensitivity</p> Signup and view all the answers

    What is the purpose of time of flight (TOF) technology in PET imaging?

    <p>To measure the time difference between the detection of two gamma rays</p> Signup and view all the answers

    What distinguishes 2D PET imaging from 3D PET imaging in terms of sensitivity to random and scatter coincidences?

    <p>3D imaging has higher sensitivity to random coincidences</p> Signup and view all the answers

    What component is used in 2D PET imaging to absorb cross plane annihilation photons and improve image quality?

    <p>Tungsten septa</p> Signup and view all the answers

    How are randoms corrected in PET imaging using the delayed coincidence sinogram method?

    <p>By holding each event for several CTWs, then regenerating the signal</p> Signup and view all the answers

    What is the main purpose of a sinogram in PET imaging?

    <p>To identify line of response (LOR) between coincident events</p> Signup and view all the answers

    What characteristic contributes to noise in PET images from a per-voxel viewpoint?

    <p>'Random and scatter count rates'</p> Signup and view all the answers

    What is the essential requirement for the detection of annihilation photons in coincidence imaging?

    <p>They must be detected in opposite detectors within a short timing window</p> Signup and view all the answers

    What happens to the annihilation photons if they are not determined to be in coincidence during a PET scan?

    <p>They are discarded</p> Signup and view all the answers

    What is the main limitation of annihilation photon imaging in PET?

    <p>Resolution variation with radionuclide used</p> Signup and view all the answers

    What is the range of units of attenuation in a CT study, expressed relative to the attenuation of water?

    <p>-1000 to +3000</p> Signup and view all the answers

    What are the approximate CT number ranges for air, soft tissue, and bone?

    <p>Air: -1000, Soft tissue: -200 - +200, Bone: +300 - +1000</p> Signup and view all the answers

    What does the term 'scatter incidents' refer to in nuclear medicine imaging?

    <p>The phenomenon where gamma rays deviate after interacting with tissues in the patient's body</p> Signup and view all the answers

    What is the main purpose of shimming coils in an MRI scanner?

    <p>To optimize the homogeneity of the magnetic field</p> Signup and view all the answers

    What refers to the ability of an imaging system to detect and accurately measure the gamma rays emitted by radioactive tracers administered to a patient?

    <p>System sensitivity</p> Signup and view all the answers

    How does pitch change the amount of radiation a patient is exposed to in CT imaging?

    <p>Higher pitch decreases radiation exposure</p> Signup and view all the answers

    What uses a 2D projection to make a 3D image in nuclear medicine imaging?

    <p>&quot;Iterative Reconstruction&quot;</p> Signup and view all the answers

    In PET imaging, what is the purpose of time of flight (TOF) technology?

    <p>To measure the time difference between the detection of two gamma rays</p> Signup and view all the answers

    What distinguishes 2D PET imaging from 3D PET imaging in terms of sensitivity to random and scatter coincidences?

    <p>3D imaging has higher sensitivity to random coincidences</p> Signup and view all the answers

    What characteristic contributes to noise in PET images from a per-voxel viewpoint?

    <p>'Random and scatter count rates'</p> Signup and view all the answers

    In coincidence imaging, what is the essential requirement for the detection of annihilation photons?

    <p>They must be detected in opposite detectors within a short timing window</p> Signup and view all the answers

    What happens to the annihilation photons if they are not determined to be in coincidence during a PET scan?

    <p>They are discarded</p> Signup and view all the answers

    Study Notes

    X-ray Tubes in CT Imaging

    • The primary purpose of the filter in an x-ray tube is to remove low-energy x-rays that are selectively absorbed by soft tissue.

    CT Number Ranges

    • Approximate CT number ranges are:
      • Air: -1000 to -900
      • Soft tissue: 0 to 100
      • Bone: 400 to 1000

    PET Imaging

    • Dead time is primarily caused by detector saturation.
    • PET images that are not attenuation corrected look very different from corrected images.
    • The biggest contributor to dead time is detector saturation.

    Coincidence Imaging

    • The purpose of detecting annihilation photons is to localize the source of the positron-emitting radionuclide.
    • If annihilation photons are not determined to be in coincidence, they are discarded.
    • The Pulse Height Analyzer ensures that only photons within a specific energy range are detected.

    Nuclear Medicine Imaging

    • SPECT uses a 2D projection to create a 3D image.
    • The septa in 2D PET imaging absorb cross-plane annihilation photons and improve image quality.
    • Time of Flight (TOF) technology improves image resolution by providing information on the time of arrival of annihilation photons.

    MRI vs. CT

    • The main advantage of MRI over CT is its superior soft tissue contrast.

    X-ray Filters

    • The filter in an x-ray tube selectively removes low-energy x-rays.

    Pitch and Radiation Exposure in CT

    • Pitch changes the amount of radiation a patient is exposed to in CT imaging by adjusting the table speed and x-ray beam width.

    Sensitivity and Coincidences

    • 2D PET imaging is less sensitive to random and scatter coincidences compared to 3D PET imaging.

    Random Correction

    • Randoms are corrected in PET imaging using the delayed coincidence sinogram method.

    Sinograms

    • The main purpose of a sinogram is to correct for random and scatter coincidences.

    Noise in PET Images

    • Noise in PET images is primarily caused by statistical fluctuations in photon detection.

    Essential Requirements

    • The essential requirement for the detection of annihilation photons is that they must be detected in coincidence by both detectors on each side.

    Limitations of Annihilation Photon Imaging

    • The main limitation of annihilation photon imaging is the low detection efficiency of annihilation photons.

    Attenuation Units

    • The range of units of attenuation in a CT study is expressed relative to the attenuation of water.

    Scatter Incidents

    • Scatter incidents refer to the detection of photons that have undergone Compton scattering.

    Shimming Coils

    • The main purpose of shimming coils in an MRI scanner is to improve the homogeneity of the magnetic field.

    Sensitivity and Detection

    • Sensitivity refers to the ability of an imaging system to detect and accurately measure the gamma rays emitted by radioactive tracers administered to a patient.

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    Description

    Test your knowledge about CT imaging and MRI with this quiz. Answer questions about x-ray filters, units of attenuation, and the type of radiation used in MRI imaging.

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