PHYSICAL CHARACTERISTICS

Xenon Xe 133 decays by beta and gamma emissions with a half-life of 5.245 days.1 Significant radiations which are emitted by the nuclide are listed in Table 1.

1

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

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.

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.

General

Xenon Xe 133, as well as other radioactive drugs, must be handled with care and appropriate safety measures should be used to minimize radiation exposure to clinical personnel. Also, care should be taken to minimize radiation exposure to patients consistent with proper patient management.

Exhaled Xenon Xe 133 Gas should be controlled in a manner that is in compliance with the appropriate regulations of the government agency authorized to license the use of radionuclides.

Radiopharmaceuticals should be used only by physicians who are qualified by training and experience in the safe use and handling of radionuclides and whose experience and training have been approved by the appropriate government agency authorized to license the use of radionuclides.

Carcinogenesis, Mutagenesis, Impairment of Fertility

No long term animal studies have been performed to evaluate carcinogenic potential or whether Xenon Xe 133 affects fertility in males or females.

Pregnancy

Animal reproductive studies have not been conducted with Xenon Xe 133 Gas. It is also not known whether Xenon Xe 133 Gas can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. Xenon Xe 133 Gas should be given to a pregnant woman only if clearly needed.

Ideally, examination using radiopharmaceuticals, especially those elective in nature in a woman of childbearing capability, should be performed during the first few (approximately 10) days following the onset of menses.

Nursing Mothers

It is not known whether Xenon Xe 133 is excreted in human milk. Many drugs are excreted in human milk, therefore formula feedings should be substituted for breast feeding, because of the potential for adverse reactions in nursing infants.

Pediatric Use

Safety and effectiveness in the pediatric population has not been established.

Geriatric Use

Clinical studies of Xenon Xe 133 Gas did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosage range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.

RADIATION DOSIMETRY

The estimated absorbed radiation doses2 to an average patient (70 kg) for pulmonary perfusion and cerebral blood flow studies from a maximum dose of 1110 MBq (30mCi) of Xenon Xe 133 in 3 liters of air are shown in Table 4.

2

Method of Calculation: A Schema for Absorbed-Dose Calculation for Biologically Distributed Radionuclides, Supplement No. 1, MIRD pamphlet No. 1, J. Nucl. Med., p.7 (1968).

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