PT - JOURNAL ARTICLE AU - Wendt, Richard AU - Ketring, Alan AU - Frank, R. Keith AU - Simon, Jim TI - <strong>Dosimetric Implications of Radionuclidic Impurities in Low-Specific-Activity Sm-153-DOTMP</strong> DP - 2022 Aug 01 TA - Journal of Nuclear Medicine PG - 2809--2809 VI - 63 IP - supplement 2 4099 - http://jnm.snmjournals.org/content/63/supplement_2/2809.short 4100 - http://jnm.snmjournals.org/content/63/supplement_2/2809.full SO - J Nucl Med2022 Aug 01; 63 AB - 2809 Introduction: Long-lived radionuclides that are incorporated into the body with a long biological half-life have the potential to impart an appreciable absorbed dose to a patent. Reactor-produced samarium-153 is known to contain several long-lived radionuclidic impurities. Efficient chelators such as 1,4,7,10­tetraaza­cyclododecane­tetra­methylene­phosponic acid (DOTMP) that are used in bone-seeking radiopharmaceuticals cause these radionuclides to be incorporated into the skeleton more or less permanently. The internal dosimetry of the radionuclidic impurities in low-specific-activity Sm-153-DOTMP was estimated in order to determine its magnitude relative to that of the Sm-153 alone.Methods: A target of enriched Sm-152 was irradiated in a flux of 8.0x1013 neutrons/cm2-sec for 48 hours at the University of Missouri Research Reactor. The resulting Sm-153 was analyzed by gamma spectroscopy after being decayed for 64 days to reduce the Sm-153 to a negligible level. The radionuclide activities were decay-corrected back to the time of production and presented as fractions of the activity of the Sm-153. Decay-corrected source organ data from a preclinical study of Sm-153-DOTMP were re-analyzed using the physical half-lives of each of the radionuclidic impurities. The decayed time-activity curves were integrated for 50 years. The resulting humanized residence times were input into OLINDA/EXM 2.2 and the target organ dose estimates were obtained for the ICRP 89 Adult Male and Adult Female models.Results: The radionuclidic impurities that were measured in the Sm-153 sample as a fraction of the Sm153 at the time of production are Gd-153 – 6.38x10-7, Eu-152 – 7.21x10-8, Eu-154 – 2.35x10-6, Eu-155 – 3.50x10-7, and Eu-156 – 1.45x10-6. The three target organs with the highest doses are the red marrow, the osteogenic cells, and the urinary bladder wall. The doses in mSv for the two ICRP 89 adult models administered 1 mCi/kg are tabulated below.Conclusions: The radionuclidic impurities in low-specific-activity Sm-153-DOTMP impart an effective dose equivalent to the patient that is less than 0.5% of that from the Sm-153. The effective dose equivalents from the impurities in a 1 mCi/kg administration have a background-equivalent radiation time of about 160 days for the male model and 150 days for the female model.