Long term retention and excretion of 201Tl in a patient after myocardial perfusion imaging

201Tl is widely used in nuclear medicine to carry out myocardial perfusion imaging (MPI). However, very limited data is available on long-term distribution in the body, excretion and corresponding dose. In this study we performed a 2 month follow-up of a patient who underwent MPI, by urine analysis and in viva measurements. The biological half-life of thallium was consequently estimated to be 11.6-27 d, which is in partial agreement with previous studies. We also estimated excretion and retention of 2 0 0 Tl, 2 0 1 Tl and 2 0 2 Tl isotopes using the biokinetic parameters from ICRP publication 53 and compared the forecast result with actual measurements. The latter demonstrated a higher urinary excretion and a higher body retention than what was expected. Our results therefore suggest that the long-term retention and consequently the effective dose coefficient for 2 0 1 Tl considered in ICRP publications 53 and 80 may be slightly underestimated.