Trace Sciences International

Thallium Isotopes

Nominal Mass
Accurate Mass
% Natural Abundance
Chemical Form
Enrichment Available %

203 Tl

202.972320 (5)

29.524 (14)

metal, oxide

82 – 99

205 Tl

204.974401(5)

70.476 (14)

metal, oxide

89 – 99

Thallium has two stable isotopes and one of these, Tl-203, is used to produce one of the “workhorses” of nuclear medicine: Tl-201. Tl-201 is used extensively for imaging and in particular for perfusion tests of the myocardium. These tests are done to determine the damage to the heart from a heart attack or from heart diseases. Tl-205 has been proposed as an alternative target for the production of Tl-201. Tl-205 is also used in nuclear magnetic resonance research.