Physics and Radiobiology of Nuclear Medicine

the transition of an electron from the next upper shell, in which case the
difference in energy between the two shells appears as a characteristic
x-ray of the daughter nuclide. Also, as described earlier, instead of charac-
teristic x-ray emission, the Auger process can occur, whereby an Auger
electron is emitted.

Questions

1. What are the primary criteria for b+and b−-decay?


2. If the energy difference between the proton-rich parent nuclide and the
   daughter nuclide is 1.2 MeV, could the parent radionuclide decay by b+-
   decay and/or electron capture? If the energy difference is 0.8 MeV, what
   should be the mode of decay?


3. If the total conversion coefficient (aT) of 195-keV g-rays of a radionu-
   clide is 0.23, calculate the percentage of 195-keV photons available for
   imaging.


4. Can a K-shell electron be emitted as an Auger electron? Explain.


5. Explain how characteristic x-rays and Auger electrons are emitted.


6. Why is an antineutrino emitted in b−-decay?


7. A K-shell electron is ejected by the internal conversion of a 155-keV
   g-ray photon. If the binding energy of the K-shell electron is 25 keV, what
   is the kinetic energy of the electron?


8. What is the average energy of the b−-particles emitted from a
   radionuclide?


9. Explain the production of annihilation radiations.

Suggested Readings

Evans RD.The Atomic Nucleus.Malabar, FL: Kreiger; 1982.
Friedlander G, Kennedy JW, Miller JM.Nuclear and Radiochemistry. 3rd ed. New
York: Wiley; 1981.
Turner JE.Atoms, Radiation, and Radiation Protection.2nd ed. New York: Wiley;
1995.

20 2. Radioactive Decay