[Estimation of radiation dose produced by impurities in nuclear medicine studies using Tl-201 chloride]

Radionuclide impurities can significantly increase the absorbed dose in Nuclear Medicine examinations. The aim of this study is to evaluate the dose of Tl-200 and Tl-202 in patients injected with Tl-201 for myocardial scintigraphy. All relevant nuclear and biological data are reported; Thallium distribution in the body is then discussed with particular regard to the gastro-intestinal tract. Since MIRD Committee has not published "S" values for Tl-200 and Tl-202, these have been calculated by a computer code and are reported. The absorbed dose for these Thallium isotopes is presented. For example, kidney doses in Gy/GBq are 0.29 (Tl-200), 0.27 (Tl-201) and 0.97 (Tl-202). The total dose increase for a 2% presence of Tl-202 is about 11%.