choline c 11 - Medications

11.1 Chemical Characteristics Choline C 11 Injection is a positron emitting radiopharmaceutical that is used for diagnostic purposes in conjunction with PET imaging. The active ingredient, 11 C-choline, has the molecular formula of C 4 11 CH 14 NOCl with a molecular weight of 138.63 g and has the following chemical structure: Choline C 11 Injection is provided as a ready to use sterile, pyrogen-free, clear and colorless solution. Each milliliter contains 148 – 1,225 MBq (4 – 33.1 mCi) of 11 C-choline at EOS calibration time in aqueous 0.9% sodium chloride solution. The pH of the solution is between 4.5 and 7.5. C-11 choline chloride structure 11.2 Physical Characteristics Carbon 11 is a cyclotron-produced radionuclide that decays to Boron 11 by positron emission and has a physical half life of 20.4 minutes (Table 2). Table 2: Principal Radiation Emission Data for 11 C Radiation/Emission % Per Disintegration Energy Positron (β+) 99.76 960.2 keV (Max.) Gamma (±)* 199.5 511 keV *Produced by positron annihilation The specific gamma ray constant (point source air kerma coefficient) for 11 C-choline is 5.8 R/mCi-hr at 1 cm. Selected coefficients of attenuation are listed in Table 3 as a function of lead shield thickness. For example, the use of 39 mm thickness of lead will attenuate the external radiation by a factor of about 1,000. Table 3: Radiation Attenuation of 511 keV Photons by lead (Pb) shielding Shield Thickness (Pb) mm Coefficient of Attenuation 4 0.5 8 0.25 13 0.1 26 0.01 39 0.001 52 0.0001 Table 4 lists fractions remaining at selected time intervals from the calibration time. This information may be used to correct for physical decay of the radionuclide. Table 4: Physical Decay Chart for 11 C Minutes Fraction Remaining 0* 1.000 5 0.844 10 0.712 15 0.600 20 0.507 25 0.427 30 0.360 *Calibration time