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Positron Emission Tomography
Angela P. Bruner, PhD, DABR
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KEY FACTS

  • Positron Emission Tomography

    • 2D and 3D Acquisition Modes

      • Attenuation Correction

        TERMINOLOGY

        • Definitions

          • Positron emission tomography (PET)
            • Imaging of 511 keV gamma photons produced after annihilation
            • Ring of detectors surrounds patient and detects coincident gamma photons emitted, creating 3D image
            • Compared to gamma camera SPECT or coincidence imaging, PET imaging has higher spatial resolution (SR), higher contrast resolution (CR), and greater sensitivity
          • Positrons (positively charged electrons)
            • Positively charged products of radioactive decay from radionuclides that are positron emitters
            • Have same mass as electrons
            • Travel short distance before combining with free electrons and annihilating; annihilation produces two 511 keV gamma ray photons
          • Positron emitter: Radionuclides that emit positrons (β⁺)
            • Positron inside nucleus transforms into neutron (which remains in nucleus) and positron and neutrino (both of which are ejected from atom)
              • Commonly, positron emitters also have small probability for electron capture: Electron combines with proton from nucleus to become neutron plus neutrino
                • e.g., F-18 has 97% probability of positron emission and 3% probability of electron capture
            • ρ⁺ (proton) → η (neutron) + β⁺ (positron) + ν (neutrino) + energy
            • Total # of protons (atomic number) decreased by 1
            • Total # of neutrons increased by 1
            • Mass # unchanged (= # of protons + # of neutrons)
          • Annihilation
            • When positron combines with electron
            • Mass of positron and electron converted to energy in form of two 511 keV gamma photons given off in opposite directions (~ 180° apart)
            • 511 keV gamma photons part of electromagnetic family (move at speed of light, have no mass, and have no charge)

        IMAGING ANATOMY

        • PET Radionuclides

          • Flow of Data and Processing

            • PET Detector Array Design

              • PET Image Quality

                Imaging Features

                • 2D Direct Imaging

                  • 2D Cross-Plane Imaging

                    • 2D High-Sensitivity Imaging

                      • 3D Imaging

                        • PET/CT

                          • PET/MR

                            • Attenuation Correction

                              • Standard Uptake Value

                                • Quality Control

                                  • Artifacts

                                    Selected References

                                    1. Ziessman HA et al. Nuclear Medicine: The Requisites, 4th Edition (Requisites in Radiology). Saunders, 2013
                                    2. Granov A et al. Positron Emission Tomography. Springer, 2013
                                    3. Chandra R. Nuclear Medicine Physics: The Basics, 7th Edition. Lippincott, Williams and Wilkins, 2012
                                    4. Bushberg JT et al. The Essential Physics of Medical Imaging, 3rd Edition. Lippincott, Williams and Wilkins, 2011
                                    5. Saha GB. Basics of PET Imaging: Physics, Chemistry, and Regulations. Springer, 2004
                                    6. Christian PE et al. Nuclear Medicine and PET: Technology and Techniques, 5th Edition. Mosby, 2004
                                    7. Valk PE et al. Positron Emission Tomography: Basic Science and Clinical Practice. Springer, 2002
                                    Related Anatomy
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                                    Related Differential Diagnoses
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                                    References
                                    Tables

                                    Tables

                                    KEY FACTS

                                    • Positron Emission Tomography

                                      • 2D and 3D Acquisition Modes

                                        • Attenuation Correction

                                          TERMINOLOGY

                                          • Definitions

                                            • Positron emission tomography (PET)
                                              • Imaging of 511 keV gamma photons produced after annihilation
                                              • Ring of detectors surrounds patient and detects coincident gamma photons emitted, creating 3D image
                                              • Compared to gamma camera SPECT or coincidence imaging, PET imaging has higher spatial resolution (SR), higher contrast resolution (CR), and greater sensitivity
                                            • Positrons (positively charged electrons)
                                              • Positively charged products of radioactive decay from radionuclides that are positron emitters
                                              • Have same mass as electrons
                                              • Travel short distance before combining with free electrons and annihilating; annihilation produces two 511 keV gamma ray photons
                                            • Positron emitter: Radionuclides that emit positrons (β⁺)
                                              • Positron inside nucleus transforms into neutron (which remains in nucleus) and positron and neutrino (both of which are ejected from atom)
                                                • Commonly, positron emitters also have small probability for electron capture: Electron combines with proton from nucleus to become neutron plus neutrino
                                                  • e.g., F-18 has 97% probability of positron emission and 3% probability of electron capture
                                              • ρ⁺ (proton) → η (neutron) + β⁺ (positron) + ν (neutrino) + energy
                                              • Total # of protons (atomic number) decreased by 1
                                              • Total # of neutrons increased by 1
                                              • Mass # unchanged (= # of protons + # of neutrons)
                                            • Annihilation
                                              • When positron combines with electron
                                              • Mass of positron and electron converted to energy in form of two 511 keV gamma photons given off in opposite directions (~ 180° apart)
                                              • 511 keV gamma photons part of electromagnetic family (move at speed of light, have no mass, and have no charge)

                                          IMAGING ANATOMY

                                          • PET Radionuclides

                                            • Flow of Data and Processing

                                              • PET Detector Array Design

                                                • PET Image Quality

                                                  Imaging Features

                                                  • 2D Direct Imaging

                                                    • 2D Cross-Plane Imaging

                                                      • 2D High-Sensitivity Imaging

                                                        • 3D Imaging

                                                          • PET/CT

                                                            • PET/MR

                                                              • Attenuation Correction

                                                                • Standard Uptake Value

                                                                  • Quality Control

                                                                    • Artifacts

                                                                      Selected References

                                                                      1. Ziessman HA et al. Nuclear Medicine: The Requisites, 4th Edition (Requisites in Radiology). Saunders, 2013
                                                                      2. Granov A et al. Positron Emission Tomography. Springer, 2013
                                                                      3. Chandra R. Nuclear Medicine Physics: The Basics, 7th Edition. Lippincott, Williams and Wilkins, 2012
                                                                      4. Bushberg JT et al. The Essential Physics of Medical Imaging, 3rd Edition. Lippincott, Williams and Wilkins, 2011
                                                                      5. Saha GB. Basics of PET Imaging: Physics, Chemistry, and Regulations. Springer, 2004
                                                                      6. Christian PE et al. Nuclear Medicine and PET: Technology and Techniques, 5th Edition. Mosby, 2004
                                                                      7. Valk PE et al. Positron Emission Tomography: Basic Science and Clinical Practice. Springer, 2002