Xenon Xe 133 Gas Description

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
*Calibration Date **Expiration Date
-5 0* 7 14**	>98.3 >98.1 >97.2 >95.7	<0.6>	<1.0>	<0.03>	<0.01>

PHYSICAL CHARACTERISTICS

Xenon Xe 133 decays by beta and gamma emissions with a physical half-life of 5.245 days.1 Photons that are useful for detection and imaging studies as well as the principal beta emission are listed in Table 2.

Table 2. Principal Radiation Emission Data

Radiation	Mean % Per Disintegration	Energy (keV)
Beta-2 Gamma-2 K alpha x-rays K beta x-rays	99.3 36.5 38.9 9.1	100.6 Avg. 81.0 30.8 Avg. 35.0 Avg.

1

Kocher, David C., "Radioactive Decay Data Tables," DOE/TIC-11026,138 (1981).