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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.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

thal·li·um (Tl),

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)]
Farlex Partner Medical Dictionary © Farlex 2012


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)]
Medical Dictionary for the Health Professions and Nursing © Farlex 2012


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.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005
References in periodicals archive ?
Editorial Note: When ingested, thallium is a systemic poison that can produce multiple organ toxicity involving the gastrointestinal, neurologic, and cardiovascular systems (2).
Compared with whites, blacks and Mexican Americans had higher levels of cadmium, lead, and tungsten, and blacks had higher levels of cesium, molybdenum, antimony, and thallium. Current smokers had higher levels of cadmium, lead, antimony, and tungsten compared with never smokers.
The thallium rest test was followed either by stressing the patient on a treadmill or pharmacologically inducing stress if the patient was incapable of exercise.
The doctors have expressed their dissatisfaction over the Thallium scan test report of the former premier.
Vetter, and their coworkers looked for parity violation in the behavior of the outermost electron of a thallium atom.
THALLIUM is a toxic metal which attacks the nervous system, lungs, heart, liver and kidneys.
This new ceramic, which they call a "defect chemistry superlattice," is made from sandwichlike layers of thallium (III) oxide.
Tests later showed he had been poisoned with deadly thallium.