thallium

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thallium

 [thal´e-um]
a chemical element, atomic number 81, atomic weight 204.37, symbol Tl. (See Appendix 6.) Its salts are active poisons that may cause alopecia, liver and kidney damage, blindness, and neurologic and psychic symptoms such as ataxia, restlessness, delirium, hallucinations, delusions, and semicoma.
thallium 201 a radioactive isotope of thallium having a half-life of 3.05 days and decaying by electron capture with emission of gamma rays. It is used as a diagnostic aid in the form of thallous chloride Tl 201.
thallium scan a scintiscan involving the use of thallium 201. The radioisotope is administered intravenously and localizes, like calcium, in the myocardium. A scintillation camera produces an image of the distribution of the radioisotope. Areas of inadequate perfusion appear as “cold spots,” thus pinpointing the site of occlusions of the coronary arteries.



The thallium scan offers many advantages. It is noninvasive except for the administration of the radioisotope, which involves a radiation dose slightly larger than that received during a chest x-ray, and is extremely accurate.

The thallium-201 may be administered while the patient is exercising on a treadmill and being monitored by electrocardiogram. Subsequent scintigrams show areas of inadequate perfusion. This test is less likely than conventional exercise or stress testing to indicate disease when none is present and is more likely to detect disease when it is present. See also exercise thallium scintigraphy and myocardial perfusion scintigraphy.

thal·li·um (Tl),

(thal'ē-ŭm),
A white metallic element, atomic no. 81, atomic wt. 204.3833; 201Tl (half-life equal to 3.038 days) is used to scan the myocardium.
[G. thallos, a green shoot (it gives a green line in the spectrum)]

thallium

/thal·li·um/ (thal´e-um) chemical element, at. no. 81, symbol Tl. It may be absorbed from the gut and from the intact skin, causing a variety of neurologic and psychic symptoms and liver and kidney damage.
thallium 201  a radioactive isotope of thallium having a half-life of 3.05 days and decaying by electron capture with emission of gamma rays (0.135, 0.167 MeV); it is used as a diagnostic aid in the form of thallous chloride Tl 201.

thallium (Tl)

[thal′ē·əm]
Etymology: Gk, thallos, green line
a soft, bluish-white metallic element that exhibits some nonmetallic chemical properties. Its atomic number is 81; its atomic mass (weight) is 204.38. Many of its compounds are highly toxic. Thallium sulfate is widely used as a rat poison.

thal·li·um

(thal'ē-ŭm)
A white metallic element; atomic no. 81, atomic wt. 204.3833; 201Tl (half-life equal to 3.038 days) is used to scan the myocardium.
[G. thallos, a green shoot (it gives a green line in the spectrum)]

thallium

A rare metallic element of which a radioactive ISOTOPE is used in RADIONUCLIDE SCANNING of the heart. Thallium scanning can reveal areas of heart muscle that are deprived of a normal blood supply as a result of coronary artery occlusion.

thallium

a chemical element, atomic number 81, atomic weight 204.37, symbol Tl. See Table 6. Its salts are active poisons. See thallotoxicosis.

thallium-201
a radioactive isotope of thallium having a half-life of 73.5 hours; the principal emission is 71 keV x-rays.
thallium poisoning
thallium scan
a scintillation scan involving the use of thallium-201 which localizes in the myocardium after intravenous injection. Areas of inadequate perfusion pinpoint the site of coronary artery occlusions.