Indium In-111 Pentetate Disodium

DESCRIPTION GE Healthcare (Medi-Physics, Inc.) Indium DTPA In 111 is a diagnostic drug for intrathecal use. It is available as a sterile, pyrogen-free, isotonic, aqueous solution, buffered to pH 7 to 8. At calibration time, each milliliter contains 37 MBq, 1 mCi of Pentetate Indium Disodium In 111 (no-carrier-added), 20 to 50 µ g of pentetic acid, and sodium bicarbonate for pH adjustment. The drug is to be discarded after single use. Radionuclidic purity at calibration time is at least 99.88% with less than 0.06% Indium In 114m and 0.06% Zinc Zn 65. The concentration of each radionuclidic contaminant changes with time. Graph 1 shows maximum concentration of each radionuclidic impurity as a function of time. Graph 1 - Radionuclidic Impurities The chemical names are 1. Indate(2-)- 111 In -[ N,N -bis[2-[bis-(carboxymethyl)amino]ethyl]glycinato(5-)]-disodium; and 2. Disodium [ N,N -bis[2-(carboxymethyl)amino]glycinato(5-)]-indate (2-) 111 In. Molecular formula: C 14 H 18 O 10 N 3 111 In Na 2 Molecular weight: 545.29 Structural formula: PHYSICAL CHARACTERISTICS Indium 111 decays by electron capture with a physical half-life of 67.9 hours. The energies of the photons that are useful for detection and imaging studies are listed in Table 1. Table 1. Principal Radiation Emission Data Kocher, David C.,"Radioactive Decay Data Tables,"DOE/TIC-11026, 115, (1981). Radiation Mean %/Disintegration Mean Energy (keV) Gamma-2 90.2 171.3 Gamma-3 94.0 245.4 EXTERNAL RADIATION The specific gamma ray constant for Indium In 111 is 3.3 R/hr-mCi at 1 cm. The half-value thickness of lead (Pb) for Indium In 111 is 0.021 cm. To facilitate control of the radiation exposure from millicurie amounts of this radionuclide, a range of values for the relative attenuation of the radiation emitted by this radionuclide that results from interposition of various thicknesses of Pb is shown in Table 2. For example, the use of a 0.8 cm thickness of Pb will attenuate the radiation emitted by a factor of about 1,000. Table 2. Radiation Attenuation by Lead Shielding Shield Thickness (Pb) cm Coefficient of Attenuation To correct for physical decay of this radionuclide, the fractions that remain at selected time intervals after the time of calibration are shown in Table 3. 0.021 0.5 0.19 10 -1 0.49 10 -2 0.80 10 -3 1.1 10 -4 Table 3. Physical Decay Chart: Indium In 111, Half-Life 67.9 Hours Hours Fraction Remaining Hours Fraction Remaining 0 Calibration Time 1.000 84 0.424 12 0.885 96 0.375 24 0.783 108 0.332 36 0.693 120 0.294 48 0.613 132 0.260 60 0.542 144 0.230 72 0.480 168 0.180 Graph 1 Structural formula