"How long a young adult is obese may affect that person's heart disease risk in middle age, according to new research. The finding suggests that not only preventing but also delaying the onset of obesity can help reduce heart disease later in life"...
Thallous Chloride Tl-201 Injection
Thallous Chloride Tl-201 Injection (thallous chloride)
Diagnostic – For Intravenous Use
Thallous Chloride Tl-201 Injection (thallous chloride) is supplied in an isotonic solution as a sterile, non-pyrogenic diagnostic radiopharmaceutical for intravenous administration. Each milliliter contains 37 megabecquerels (1 millicurie) Thallous Chloride Tl-201 at calibration time, made isotonic with 9 milligrams sodium chloride and preserved with 0.9% (v/v) benzyl alcohol. The pH is adjusted to between 4.5 to 7.0 with hydrochloric acid and/or sodium hydroxide. Thallium Tl-201 is cyclotron produced. At the time of calibration it contains no more than 1.0% Thallium Tl-200, no more than 1.0% Thallium Tl-202, no more than 0.25% Lead Pb-203, and no less than 98% Thallium Tl-201 as a percentage of total activity. No carrier has been added.
It is recommended that Thallous Chloride Tl-201 be administered close to calibration time to minimize the effect of higher levels of radionuclidic contaminants present at pre- and post-calibration dates. The concentration of each radionuclidic contaminant changes with time. Figure 1 shows maximum concentration of each radionuclidic contaminant as a function of time.
Figure 1. Radionuclidic Contaminants
Thallium Tl-201, with a physical half life of 73.1 hours, decays by electron capture to mercury Hg 201.1 Photons that are useful for detection and imaging are listed in Table 1. The lower energy x-rays obtained from the mercury Hg 201 daughter of thallium Tl-201 are recommended for myocardial imaging, because the mean percent disintegration at 68.9 to 80.3 keV is much greater than the combination of gamma-4 and gamma-6 mean percent disintegration.
Table 1. Principal Radiation Emission Data
|Radiation||MeanPercent/ Disintegration||Energy (keV)|
The specific gamma ray constant for thallium Tl-201 is 4.7 R/mCi-hr2 at 1 cm. The first half-value thickness of lead (Pb) is 0.0006 cm. A range of values for the radiation emitted by this radionuclide with the corresponding exposure rate at 1 cm that results from interposition of various thicknesses of lead is shown in Table 2. For example, the use of 0.21 cm of lead will decrease the external radiation exposure by a factor of about 1,000.
Table 2. Radiation Attenuation by Lead Shielding
|cm of Lead(Pb)||Coefficient of Attenuation|
To correct for physical decay of the radionuclide, the fractions that remain at selected intervals after calibration time are shown in Table 3.
Table 3. Thallium Tl-201 Decay Chart; Half-Life 73.1 Hours
|Hours||Fraction Remaining||Hours||Fraction Remaining|
1. Kocher, David C., "Radioactive Decay Data Tables," DOE/TIC- 11026, 181 (1981).
2. Includes 10 keV x-rays.
Last reviewed on RxList: 10/21/2008
This monograph has been modified to include the generic and brand name in many instances.
Additional Thallous Chloride Tl-201 Injection Information
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
Get the latest treatment options.