xenon xe 133 - Medications

Xenon Xe 133 Gas is supplied in a mixture of xenon gas (5%) in carbon dioxide (95%). It is contained within septum sealed glass vials and is suitable for inhalation in the diagnostic evaluation of pulmonary function and imaging, as well as assessment of cerebral blood flow. Xenon Xe 133 Gas is reactor-produced as a by-product of Uranium U235 fission. Each vial contains the labeled amount of Xenon Xe 133 radioactivity at the time of calibration. The contents of the vial are in gaseous form, contain no preservatives, and are ready for use. Xenon Xe 133 is chemically and physiologically related to elemental Xenon, a non-radioactive monoatomic gas which is physiologically inert except for anesthetic properties at high doses. PHYSICAL CHARACTERISTICS Xenon Xe 133 decays by beta and gamma emissions with a half-life of 5.245 days. Kocher, David C., "Radioactive Decay Data Tables," DOE/TIC-11026, p. 138,1981. Significant radiations which are emitted by the nuclide are listed in Table 1. Table 1. Principal Radiation Emission Data from Xenon-133 Mean Mean % per Radiation Energy (KeV) Disintegration Beta-2 100.6 99.3 Ce-K-2 45.0 53.3 Ce-L-2 75.3 8.1 Ce-M-2 79.8 1.7 Gamma-2 81.0 36.5 K α2 X-ray 30.6 13.6 K α1 X-ray 31.0 25.3 K β X-ray 35.0 9.1 EXTERNAL RADIATION The specific gamma ray constant for Xenon Xe 133 is 3.6 microcoulombs/Kg-MBq-hr (0.51R/hr-mCi) at 1 cm. The first half value thickness of lead is 0.0035 cm. A range of values for the relative attenuation of the radiation emitted by this radionuclide that results from the interposition of various thicknesses of Pb is shown in Table 2. For example, the use of 0.20 cm of Pb will decrease the external radiation exposure by a factor of 1,000. Table 2. Radiation Attenuation by Lead Shielding cm of Pb Radiation Attenuation Factor 0.0035 0.5 0.037 10 -1 0.12 10 -2 0.20 10 -3 0.29 10 -4 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. Table 3. Xenon Xe 133 Physical Decay Chart (Half Life 5.245 days) Fraction Fraction Day Remaining Day Remaining 0 Calibration Day 1.000 8 .349 1 .877 9 .302 2 .768 10 .268 3 .674 11 .235 4 .591 12 .206 5 .518 13 .181 6 .452 14 .157 7 .398

Xenon Xe 133 Gas is for diagnostic inhalation use only. It is supplied in vials containing either 370 or 740 megabecquerels (10 or 20 millicuries) of Xenon Xe 133 Gas in 2 milliliters of carrier xenon and atmospheric air. Xenon Xe 133 Gas is chemically and physiologically similar to elemental xenon, a non-radioactive gas which is physiologically inert except for anesthetic properties at high doses. Xenon Xe 133 is produced by fission of Uranium U 235. At the time of calibration, it contains no more than 0.3% Xenon Xe 133m, no more than 1.5% Xenon Xe 131m, no more than 0.06% Krypton Kr 85 and no more than 0.01% Iodine I 131, with no less than 99.9% total radioactivity as radioxenon. Table 1 shows the effect of time on radionuclidic composition. Table 1. Radionuclidic Composition Percent of Total Radioactivity Days % Xe-133 % Xe-133m % Xe-131m % Kr-85 % I-131 -5 >98.3 <0.6 <1.0 <0.03 <0.01 0 Calibration Date >98.1 <0.3 <1.5 <0.06 <0.01 7 >97.2 <0.08 <2.5 <0.15 <0.02 14 Expiration Date >95.7 <0.02 <4.1 <0.37 <0.02