Gamma Camera Scintillators for Medical Imaging
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Questions and Answers

Why is it important for a scintillator to have a high atomic number?

  • To reduce the decay time
  • To enhance imaging performance for clinical use (correct)
  • To increase refraction index
  • To minimize the cost

    • What is a limitation of Sodium Iodide (NaI) scintillators?

  • High cost
  • Low light output
  • Long decay time
  • Moisture absorption and fragility (correct)

    • What is the primary reason for sealing NaI crystals in airtight containers?

  • To reduce their decay time
  • To increase their light output
  • To prevent moisture absorption (correct)
  • To reduce their cost

    • What is the density of CsI(Na) scintillators?

    <p>4.51 g/cm³</p> Signup and view all the answers

    What is the peak emission wavelength of CsI(Tl) scintillators?

    <p>540 nm</p> Signup and view all the answers

    What is the refraction index of Na(Tl) scintillators?

    <p>1.85</p> Signup and view all the answers

    Why is it important for a scintillator to have a short decay time?

    <p>To enhance imaging performance</p> Signup and view all the answers

    What is the most widely used scintillator in conventional gamma ray imaging systems?

    <p>NaI scintillators</p> Signup and view all the answers

    What shapes can holes in collimators be manufactured in?

    <p>Triangular, square, or circular</p> Signup and view all the answers

    What is the typical range of thickness for parallel hole collimators used in traditional gamma cameras?

    <p>25-80 mm</p> Signup and view all the answers

    What is the structure of parallel bore arrays?

    <p>Symmetrical with identical holes</p> Signup and view all the answers

    At what angle do incident gamma photons pass through the parallel hole collimator?

    <p>Perpendicular angle</p> Signup and view all the answers

    What is a benefit of parallel hole collimators compared to pinhole collimators?

    <p>Superior level of sensitivity</p> Signup and view all the answers

    What happens to off-axis gamma photons in gamma imaging systems?

    <p>They are absorbed by the collimator body</p> Signup and view all the answers

    Why do larger hole diameters in parallel hole collimators degrade spatial resolution?

    <p>Because they allow a wider range of acceptance angles</p> Signup and view all the answers

    What is a key factor in determining the septal thickness of a parallel-hole collimator?

    <p>The energy of the gamma photons</p> Signup and view all the answers

    What is the use of medium-energy collimators?

    <p>Up to 400 keV</p> Signup and view all the answers

    What is the limitation of conventional planar gamma imaging?

    <p>Loss of depth information</p> Signup and view all the answers

    What are the two methods of emission tomography?

    <p>SPECT and PET</p> Signup and view all the answers

    What is the function of a parallel hole collimator in SPECT?

    <p>To acquire views from different directions</p> Signup and view all the answers

    How many views are taken in a SPECT scan?

    <p>60 views</p> Signup and view all the answers

    What is the approximate total scanning time for a SPECT scan?

    <p>30 minutes</p> Signup and view all the answers

    How many counts are acquired in a SPECT scan?

    <p>3 million counts</p> Signup and view all the answers

    What is the purpose of emission tomography?

    <p>To improve contrast and regain depth information</p> Signup and view all the answers

    What is the benefit of using a dual- or triple-headed camera in SPECT?

    <p>Halved image acquisition time or improved sensitivity</p> Signup and view all the answers

    What is the purpose of using an elliptical orbit in SPECT?

    <p>To minimize the gap between the collimator and the patient</p> Signup and view all the answers

    What is a useful option for cardiac tomography in SPECT?

    <p>180° rotation</p> Signup and view all the answers

    What can be done with the increased sensitivity in SPECT?

    <p>Increase patient throughput or improve resolution</p> Signup and view all the answers

    How can SPECT studies be presented?

    <p>Either as a series of slices or as a 3-D display</p> Signup and view all the answers

    What makes the 3-D display particularly effective in SPECT?

    <p>Persistence of vision</p> Signup and view all the answers

    What is a major use of SPECT?

    <p>Thallium studies of myocardial infarctions and ischaemia</p> Signup and view all the answers

    What is another major use of SPECT?

    <p>Quantitative cerebral blood flow</p> Signup and view all the answers

    What is the required pinhole diameter for small animal gamma imaging systems?

    <p>1-2 mm</p> Signup and view all the answers

    What is the purpose of using a non-parallel hole collimator?

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

    What is the characteristic of a low-energy collimator?

    <p>Thin septa and high sensitivity</p> Signup and view all the answers

    What is the resolution of a general purpose collimator at 10 cm from the face?

    <p>9 mm</p> Signup and view all the answers

    What is the characteristic of a high-resolution collimator?

    <p>More and smaller holes</p> Signup and view all the answers

    What is the trade-off of using a high-resolution collimator?

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

    What is the characteristic of a high-sensitivity collimator?

    <p>Fewer and larger holes</p> Signup and view all the answers

    What is the consequence of using a high-sensitivity collimator?

    <p>Lower resolution</p> Signup and view all the answers

    What is the main reason for using a medium-energy collimator?

    <p>To image radionuclides with energy up to 400 keV</p> Signup and view all the answers

    What is the primary limitation of conventional planar gamma imaging?

    <p>Insufficient depth information</p> Signup and view all the answers

    What is the purpose of rotating the gamma camera in SPECT imaging?

    <p>To acquire views from different directions</p> Signup and view all the answers

    What is the main difference between SPECT and PET imaging?

    <p>SPECT acquires single-photon emissions, while PET acquires positron emissions</p> Signup and view all the answers

    What is the purpose of emission tomography in radionuclide imaging?

    <p>To provide depth information and improve contrast</p> Signup and view all the answers

    What is the primary function of a multi-hole collimator in gamma imaging?

    <p>To delineate the image from the patient</p> Signup and view all the answers

    What is the role of a scintillation crystal in gamma imaging?

    <p>To convert gamma rays into optical light</p> Signup and view all the answers

    What is the result of gamma rays being detected by a gamma camera?

    <p>A graphical representation of the radioactive distribution is created</p> Signup and view all the answers

    What is the purpose of a gamma camera in medical imaging?

    <p>To produce a medical gamma image</p> Signup and view all the answers

    What is the energy of the gamma rays emitted by the radionuclide 99mTc?

    <p>141keV</p> Signup and view all the answers

    What is the typical thickness range for scintillators in gamma cameras?

    <p>6 to 12.5 mm</p> Signup and view all the answers

    What happens when gamma photons interact with the scintillation crystal?

    <p>The energy is deposited and converted to visible optical photons</p> Signup and view all the answers

    What is the role of the photomultiplier tube (PMT) in gamma detection?

    <p>To convert optical photons into an electrical signal</p> Signup and view all the answers

    What is the wavelength of optical photons transmitted by the NaI scintillator?

    <p>415 nm</p> Signup and view all the answers

    What is the relationship between the electric current and the number of detected optical photons in a PMT?

    <p>Directly proportional</p> Signup and view all the answers

    What is the benefit of using a dual- or triple-headed camera in SPECT?

    <p>Reduced image acquisition time or improved sensitivity</p> Signup and view all the answers

    Why is an elliptical orbit sometimes used in SPECT?

    <p>To minimize the gap between the collimator and the patient</p> Signup and view all the answers

    How can SPECT studies be presented?

    <p>Either as a series of slices or as a three-dimensional display</p> Signup and view all the answers

    What is a useful option for cardiac tomography in SPECT?

    <p>A 180° rotation</p> Signup and view all the answers

    What can be done with the increased sensitivity in SPECT?

    <p>Use the increased sensitivity for faster patient throughput or to improve the resolution</p> Signup and view all the answers

    What is the purpose of a dynode in a photomultiplier tube?

    <p>To amplify the electrons produced by the photocathode</p> Signup and view all the answers

    What is the result of the collision between the primary electrons and the dynode surface in a photomultiplier tube?

    <p>The liberation of more electrons</p> Signup and view all the answers

    What is the purpose of minimizing scattered gamma photons in gamma imaging?

    <p>To reduce the noise in the gamma image</p> Signup and view all the answers

    What is the outcome of the cascade procedure in a photomultiplier tube?

    <p>The collection of electrons at the anode</p> Signup and view all the answers

    What is formed on a pixelated grid in a conventional gamma camera?

    <p>A gamma image</p> Signup and view all the answers

    What is the purpose of quality control in radiopharmaceuticals?

    <p>To ensure the correct labelling of compounds</p> Signup and view all the answers

    What is the primary function of the radiopharmaceutical in planar imaging?

    <p>To concentrate in the organ or tissues of interest</p> Signup and view all the answers

    What is tested during quality control for radionuclide purity?

    <p>Contamination with 99Mo</p> Signup and view all the answers

    What is the purpose of the dose calibrator?

    <p>To calibrate the detector against a standard source</p> Signup and view all the answers

    What is the benefit of using an automated synthesis device for PET tracers' production?

    <p>Reduces the radiation exposure of staff</p> Signup and view all the answers

    What is the effect of using thick crystals in scintillators?

    <p>Higher sensitivity levels</p> Signup and view all the answers

    What occurs when incident gamma photons interact with the scintillator material?

    <p>An energetic electron is released</p> Signup and view all the answers

    What is a key factor influencing the scintillation process?

    <p>Crystal design</p> Signup and view all the answers

    What happens to the electrons in an excited state in the scintillator?

    <p>They return to their stable state, releasing energy as optical photons</p> Signup and view all the answers

    What is the result of Compton scattering interactions in the scintillator?

    <p>The release of energetic electrons</p> Signup and view all the answers

    What influences the type of collimator used in nuclear scanning?

    <p>Desired level of sensitivity and spatial resolution</p> Signup and view all the answers

    What is the main drawback of using collimators in gamma imaging?

    <p>Gamma photons passing through the collimator’s holes only can be registered</p> Signup and view all the answers

    What is the typical structure of parallel hole collimators?

    <p>Hexagonal structured holes in a close-packed hexagonal array</p> Signup and view all the answers

    What is the benefit of using a parallel hole collimator in gamma imaging?

    <p>Maximisation of exposed area of the gamma camera detector</p> Signup and view all the answers

    What is the primary goal of emission tomography in radionuclide imaging?

    <p>To produce a 3D image of the body</p> Signup and view all the answers

    What is a major application of SPECT imaging?

    <p>Cardiac tomography</p> Signup and view all the answers

    How does the parallel hole collimator differ from other collimators?

    <p>It has hexagonal structured holes</p> Signup and view all the answers

    What is the advantage of using a high-density material plate in parallel hole collimators?

    <p>Higher absorption of gamma rays</p> Signup and view all the answers

    What influences the design of collimators in gamma imaging?

    <p>Desired level of sensitivity and spatial resolution</p> Signup and view all the answers

    What is the benefit of using a scintillator in gamma imaging?

    <p>It converts gamma rays to visible light</p> Signup and view all the answers

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