Patton JA.
Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, TN 37232-2675, USA.
Radiographics. 1998 Jul-Aug;18(4):995-1007
Photons for counting or imaging applications in nuclear medicine result from several processes. Gamma rays are produced from excited state transitions after beta decay and electron capture. Annihilation photons result from positron decay. The de-excitation of the atom after electron capture results in the production of characteristic x rays or Auger electrons. Metastable state transitions result in gamma ray emission or internal conversion electrons. All radiopharmaceuticals used in diagnostic nuclear medicine applications are tagged with radionuclides that emit photons as a result of one of these processes.