PET Iterative Reconstruction and Image Artifacts Quiz
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Questions and Answers

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

  • They must be detected in the same detector
  • They must be detected within a long timing window
  • They must be detected in opposite detectors within a short timing window (correct)
  • They must be detected without using a Coincidence Timing Circuit

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

  • They are used for creating PET images
  • They are discarded (correct)
  • They are added to image memory
  • They are sent to the Coincidence Timing Circuit again

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

  • F-18
  • O-15
  • C-11
  • Rb-82 (correct)

    • 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>Identifying 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 reduce the chances of false coincidences</p> Signup and view all the answers

    What is the important characteristic of the scintillation materials used for coincidence imaging?

    <p>High sensitivity to 511 keV photons</p> Signup and view all the answers

    What is the chief benefit of time-of-flight (TOF) technology in PET imaging?

    <p>Improved signal-to-noise ratio (SNR)</p> Signup and view all the answers

    Which factor has a significant impact on the standardized uptake value (SUV) for FDG in PET imaging?

    <p>Uptake in other tissues</p> Signup and view all the answers

    How do the annihilation photons differ from the positron emission in terms of location?

    <p>They are emitted 180º opposed from the positron emission location</p> Signup and view all the answers

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

    <p>To remove low-energy x-rays from the beam</p> Signup and view all the answers

    In PET imaging, what is the consequence of dead time?

    <p>Loss of true coincidence</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 type of image looks very different from non-attenuation corrected images in PET?

    <p>Attenuation corrected image</p> Signup and view all the answers

    Which concept in CT imaging involves the table moving through the gantry as the gantry rotates around the table?

    <p>Helical scanning</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 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 type of radiation does MRI use to generate detailed images of internal structures?

    <p>Radiofrequency pulses</p> Signup and view all the answers

    What type of gas filled administration requires a negative pressure room?

    <p>Xe 133</p> Signup and view all the answers

    What is used to make the liquid DTPA a breathable aerosol in aerosol administration?

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

    What is used to absorb the Xenon gas during the washout phase in gas administration?

    <p>Charcoal</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

    In a CT study, what is the range of attenuation units for air?

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

    What does CT employ to create cross-sectional images of the body?

    <p>X-rays</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 is the biggest contributor to dead time in PET/CT imaging?

    <p>Single events</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 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 is the function of RF coils in an MRI scanner?

    <p>To transmit radiofrequency pulses into the body</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

    What is the main reason for attenuation being more of a problem in PET than in SPECT?

    <p>The requirement that both annihilation photons be detected</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 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 is the essential requirement for event detection in PET imaging?

    <p>Detection of two annihilation photons within the coincidence timing window (CTW) and in two blocks allowed to be in coincidence</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 scintillation crystal with the highest detection efficiency but has a long decay time and low scintillation light yield?

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

    In coincidence imaging, what represents a true coincidence event?

    <p>Two annihilation photons from a single annihilation interaction detected within the CTW</p> Signup and view all the answers

    Why is attenuation more of a problem in PET than in SPECT?

    <p>PET requires both annihilation photons to be detected</p> Signup and view all the answers

    What is the main purpose of Time of Flight (TOF) technology in PET imaging?

    <p>To improve spatial resolution of the reconstructed image</p> Signup and view all the answers

    What distinguishes PET as more quantitative than SPECT?

    <p>PET allows measurement of physiologic quantities in vivo</p> Signup and view all the answers

    Which type of coincidence originates from a single annihilation interaction and represents a true coincidence event?

    <p>True coincidence</p> Signup and view all the answers

    How is a sinogram used to evaluate motion in PET imaging?

    <p>By evaluating motion through stacking rows from each projection in a 2D image matrix</p> Signup and view all the answers

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

    <p>Detection by both detectors on each side</p> Signup and view all the answers

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

    <p>Determining if annihilation photons are in coincidence</p> Signup and view all the answers

    What distinguishes PET as more quantitative than SPECT?

    <p>Ability to detect single annihilation interactions</p> Signup and view all the answers

    What is the chief benefit of time-of-flight (TOF) technology in PET imaging?

    <p>Improved spatial resolution</p> Signup and view all the answers

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

    <p>Attenuation correction errors</p> Signup and view all the answers

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

    <p>Deflection of annihilation photons from their original path</p> Signup and view all the answers

    What is used to absorb the Xenon gas during the washout phase in gas administration?

    <p>Charcoal filter</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>Lead septa</p> Signup and view all the answers

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

    <p>By subtracting the delayed coincidence events</p> Signup and view all the answers

    What type of gas filled administration requires a negative pressure room?

    <p>Xenon gas administration</p> Signup and view all the answers

    What is the main purpose of the Coincidence Timing Circuit in coincidence imaging?

    <p>To determine if the annihilation photons are in coincidence</p> Signup and view all the answers

    Which component is responsible for identifying the annihilation photons in coincidence imaging?

    <p>Pulse Height Analyzer</p> Signup and view all the answers

    What characteristic differentiates the location of annihilation from the location of positron emission?

    <p>They differ slightly in location</p> Signup and view all the answers

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

    <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 main advantage of time-of-flight (TOF) technology in PET imaging?

    <p>Improved spatial resolution</p> Signup and view all the answers

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

    <p>Detection of non-annihilation photons</p> Signup and view all the answers

    What type of gas filled administration requires a negative pressure room?

    <p>$Xe$ administration</p> Signup and view all the answers

    'Dead time' in PET/CT imaging refers to:

    <p>$Time period during which the detector cannot record another event$</p> Signup and view all the answers

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

    <p>Single Photon Emission Computed Tomography (SPECT)</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 component is used in 2D PET imaging to absorb cross plane annihilation photons and improve image quality?

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

    Study Notes

    Coincidence Imaging

    • In coincidence imaging, the essential requirement for the detection of annihilation photons is that they are detected by both detectors on each side.
    • Annihilation photons not determined to be in coincidence during a PET scan are discarded.
    • The energy of the annihilation photons emitted from positron-emitting radionuclides is 511 keV.
    • The role of the Pulse Height Analyzer is to identify the annihilation photons in coincidence imaging.

    Radionuclides

    • Thallium-201 is not cyclotron produced and is used for Myocardial perfusion imaging.

    PET Imaging

    • The chief benefit of time-of-flight (TOF) technology is improved image resolution.
    • The consequence of dead time is reduced image quality.
    • The main limitation of annihilation photon imaging in PET is scatter incidents.
    • Attenuation corrected images look very different from non-attenuation corrected images.

    CT Imaging

    • The primary purpose of the filter in an x-ray tube is to remove low-energy x-rays.
    • The concept of helical scanning involves the table moving through the gantry as the gantry rotates around the table.
    • The filter selectively removes low-energy x-rays.
    • The range of units of attenuation in a CT study is -1000 to +1000, expressed relative to the attenuation of water.
    • Air has a range of attenuation units from -900 to -1000.
    • CT employs x-rays to create cross-sectional images of the body.
    • The approximate CT number ranges for air, soft tissue, and bone are -1000, 0-100, and 1000-3000, respectively.

    MRI Imaging

    • MRI uses magnetic fields and radio waves to generate detailed images of internal structures.
    • The main advantage of MRI over CT is its ability to provide detailed images without ionizing radiation.

    Gas Administration

    • Xenon gas administration requires a negative pressure room.
    • The washout phase of gas administration involves absorbing the Xenon gas using charcoal.
    • Oxygen is used to make the liquid DTPA a breathable aerosol.

    Other

    • The term 'scatter incidents' refers to the scattering of gamma rays by surrounding tissue.
    • The purpose of shimming coils is to correct for magnetic field inhomogeneities.
    • The function of RF coils is to transmit and receive radio signals.
    • The ability of an imaging system to detect and accurately measure gamma rays is referred to as sensitivity.
    • Pitch change in CT imaging affects the amount of radiation a patient is exposed to.
    • 2D PET imaging uses a 2D projection to make a 3D image.
    • The main reason for attenuation being more of a problem in PET than in SPECT is the longer distance traveled by the annihilation photons.
    • The purpose of time of flight (TOF) technology is to improve image resolution.
    • The delayed coincidence sinogram method is used to correct for randoms in PET imaging.
    • The main purpose of a sinogram is to evaluate motion in PET imaging.

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    Test your knowledge of positron emission tomography (PET) iterative reconstruction, noise, dead time, and attenuation. Learn about the consequences of dead time and the impact of attenuation on image quality.

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