Estimation of internal radiation due to the administration of 201Tl

Today, radioactive pharmaceuticals are widely used for the purpose of diagnosis in the field of nuclear medicine, bringing many bits of useful information. On the other hand, radiation is known to be bionegative, having possibility of inducing stochastic effects such as cancers and genetic effects even in the relatively low dose region together with non-stochastic effects which could result from radiation exposure higher than threshold value. The authors have published a series of papers with regard to the estimation of radiation exposures for medical use based on three principles for radiation protection stated in the ICRP publication 26, i.e., the principles of justification, optimization and limitation. In this paper, radiation dose by a radiation worker due to 201Tl administration for the diagnosis of acardiac disease was evaluated based on the measurement of concentration of radioactive isotope excreted in urine over 1 month. Internal radiation dose due to the administration of 3 mCi (1.11x108 Bq) of 201Tl was estimated to be 610 mrem (6.1 mSv) which agreed well with the result reported by H.L. Atkins (1977) and far exceeded the occupational exposure (approximately 60 mrem over 12 years). The authors suggested the importance of reducing medical exposure. (author)