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Basic Physics and Radionuclides
Angela P. Bruner, PhD, DABR; John Bailey, MD; Umesh D. Oza, MD
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KEY FACTS

  • Isotope Identification

    • Terminology

      TERMINOLOGY

      • Definitions

        • Atom
          • Collection of protons and neutrons in nucleus with orbiting electrons
          • Bohr model simplification is adequate for nuclear medicine, though atoms actually have quantum orbitals
          • Z: Atomic number: Number of protons
          • A: Atomic mass: Number of protons + neutrons 
            • Proton: 1.00728 atomic mass unit (amu)
            • Neutron: 1.00867 amu
            • Electron: 0.000549 amu (much smaller than proton or neutron and thus not significant part of atomic mass)
        • Isotope 
          • One of multiple forms of atom (equal in proton count; variable number of neutrons)
          • Stable isotopes have similar numbers of neutrons and protons and are not radioactive
            • Most elements (up to Pb) have > 1 stable isotope
          • Unstable isotopes (all isotopes of elements beyond Pb) have higher number of neutrons and are radioactive
            • Larger elements require more neutrons to hold nucleus together
            • Neutron-to-proton (n/p) ratio is > 1
        • Radiation 
          • In general, radiation is any emission of energy or energetic particle
          • Specific particles emitted from unstable elements that are used in nuclear medicine include alpha (α), beta (β), positron (β+), and gamma (γ) radiation
          • X-rays are also created from secondary interactions with electron shell of atom
          • X-rays are lower energy subset of gamma rays
        • Radioactive decay
          • Unstable radionuclides try to become stable by releasing particle or emission of high-energy photon
          • For lighter nuclides, stable nuclides have approximately same number of neutrons and protons
          • For heavier nuclides, stable nuclides have ~ 1.5x as many neutrons as protons
          • Becquerel (Bq) [Standard International (SI) unit] = 1 disintegration per second (dps)
          • Curie (non-SI unit) = 37 trillion dps = 37 billion Bq; 1 mCi = 37 MBq

      Radioactive Decay

      • General Concepts

        • Modes of Decay

          Radiopharmaceutical Production

          • Radionuclides 

            • Radiopharmacy

              • Quality Control 

                Selected References

                1. Mettler et al: Essentials of Nuclear Medicine and Molecular Imaging. Elsevier, 2018
                2. Cherry et al. Physics in Nuclear Medicine. Saunders, 2012
                Related Anatomy
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                References
                Tables

                Tables

                KEY FACTS

                • Isotope Identification

                  • Terminology

                    TERMINOLOGY

                    • Definitions

                      • Atom
                        • Collection of protons and neutrons in nucleus with orbiting electrons
                        • Bohr model simplification is adequate for nuclear medicine, though atoms actually have quantum orbitals
                        • Z: Atomic number: Number of protons
                        • A: Atomic mass: Number of protons + neutrons 
                          • Proton: 1.00728 atomic mass unit (amu)
                          • Neutron: 1.00867 amu
                          • Electron: 0.000549 amu (much smaller than proton or neutron and thus not significant part of atomic mass)
                      • Isotope 
                        • One of multiple forms of atom (equal in proton count; variable number of neutrons)
                        • Stable isotopes have similar numbers of neutrons and protons and are not radioactive
                          • Most elements (up to Pb) have > 1 stable isotope
                        • Unstable isotopes (all isotopes of elements beyond Pb) have higher number of neutrons and are radioactive
                          • Larger elements require more neutrons to hold nucleus together
                          • Neutron-to-proton (n/p) ratio is > 1
                      • Radiation 
                        • In general, radiation is any emission of energy or energetic particle
                        • Specific particles emitted from unstable elements that are used in nuclear medicine include alpha (α), beta (β), positron (β+), and gamma (γ) radiation
                        • X-rays are also created from secondary interactions with electron shell of atom
                        • X-rays are lower energy subset of gamma rays
                      • Radioactive decay
                        • Unstable radionuclides try to become stable by releasing particle or emission of high-energy photon
                        • For lighter nuclides, stable nuclides have approximately same number of neutrons and protons
                        • For heavier nuclides, stable nuclides have ~ 1.5x as many neutrons as protons
                        • Becquerel (Bq) [Standard International (SI) unit] = 1 disintegration per second (dps)
                        • Curie (non-SI unit) = 37 trillion dps = 37 billion Bq; 1 mCi = 37 MBq

                    Radioactive Decay

                    • General Concepts

                      • Modes of Decay

                        Radiopharmaceutical Production

                        • Radionuclides 

                          • Radiopharmacy

                            • Quality Control 

                              Selected References

                              1. Mettler et al: Essentials of Nuclear Medicine and Molecular Imaging. Elsevier, 2018
                              2. Cherry et al. Physics in Nuclear Medicine. Saunders, 2012