Axumin

11 DESCRIPTION 11.1 Chemical Characteristics Axumin contains the fluorine 18 (F 18) labeled synthetic amino acid analog fluciclovine.‍‍‍‍‍‍​​​‍​​​​​​ Fluciclovine F 18 is a radioactive diagnostic agent used with PET imaging. Chemically, fluciclovine F 18 is (1r, 3r)-1-amino-3[ 18 F]fluorocyclobutane-1-carboxylic acid. The molecular weight is 132.1 and the structural formula is: Axumin is a sterile, non-pyrogenic, clear, colorless, hyperosmolal (approximately 500 mOsm/kg to 540 mOsm/kg) injection for intravenous use. Each milliliter contains up to 2 micrograms of fluciclovine, 335 MBq to 8,200 MBq (9 mCi to 221 mCi) fluciclovine F 18 at calibration time and date, and 20 mg trisodium citrate in water for injection. The solution also contains hydrochloric acid, sodium hydroxide and has a pH between 4 and 6. Structural Formula 11.2 Physical Characteristics Fluorine 18 (F 18) is a cyclotron produced radionuclide that decays by positron emission (ß+ decay, 96.7%) and orbital electron capture (3.3%) to stable oxygen 18 with a physical half-life of 109.7 minutes. The positron can undergo annihilation with an electron to produce two gamma rays; the energy of each gamma ray is 511 keV ( Table 2 ). Table 2: Principal Radiation Produced from Decay of Fluorine 18 Radiation Energy (keV) Abundance (%) Positron 249.8 96.7 Gamma 511.0 193.5 11.3 External Radiation The point source air-kerma coefficient for F 18 is 3.75 x 10 -17 Gy m 2 /(Bq s). The first half-value thickness of lead (Pb) for F 18 gamma rays is approximately 6 mm. The relative reduction of radiation emitted by F 18 that results from various thicknesses of lead shielding is shown in Table 3 . The use of 8 cm of Pb will decrease the radiation transmission (i.e., exposure) by a factor of about 10,000. Table 3: Radiation Attenuation of 511 keV Gamma Rays by Lead Shielding Shield Thickness cm of Lead (Pb) Coefficient of Attenuation 0.6 0.5 2 0.1 4 0.01 6 0.001 8 0.0001