(redirected from thallium-201)
Also found in: Dictionary, Thesaurus, Acronyms, Encyclopedia.


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 ?
Reverse redistribution of thallium-201: a sign of non-transmural myocardial infarction with patency of the infarct-related coronary artery.
* Stress-induced moderate perfusion defect with LV dilatation or increased lung uptake (of thallium-201).
ETT is based on exercise induced membrane potential changes depicted on electrocardiography during calibrated exercise following standard protocols; while MPS is based on the delivery of a radiotracer (Thallium-201 or Technetium-99 m labelled radiopharmaceuticals) to a metabolically active substrate (myocardium) through an intact vascular system.
Becker, "Wiener filtering improves quantification of regional myocardial perfusion with thallium-201 SPECT," Journal of Nuclear Medicine, vol.
infusion of ribose, an adenine nucleotide precursor, postischemia facilitates thallium-201 (201Tl) redistribution and improves identification of ischemic myocardium in patients with coronary artery disease (CAD), 17 patients underwent two exercise 201Tl stress tests, performed 1-2 wk apart.
Cell membrane integrity can be evaluated by assessing delayed thallium-201 uptake (1,6) or the exclusion of magnetic resonance imaging (MRI) contrast in delayed images (7-9) (absence of delayed hyperenhancement).
Myocardial perfusion imaging using thallium-201 in women has a higher incidence of false-positive results than technetium-99m sestamibi scanning.
Nuclear imaging uses radiotracers (thallium-201, technetium-99m tetrofosmin (Myoview), or technetium-99m sestamibi [Cardiolite]) to evaluate myocardial perfusion and function, and has greatly advanced the ability to detect and assess the extent of CHD.
Thallium-201 chloride uptake tumors: a possible complication in heart scintigraphy.