Today, 44Sc is an attractive radionuclide for molecular imaging with PET. In this work, we evaluated a 44Ti/44Sc radionuclide generator based on TEVA resin as a source of 44Sc. The generator prototype (5 MBq) exhibits high 44Ti retention and stable yield of 44Sc (91 ± 6 %) in 1 mL of eluate (20 bed volumes, eluent—0.1 M oxalic acid/0.2 M HCl) during one year of monitoring (more than 120 elutions). The breakthrough of 44Ti did not exceed 1.5 × 10−5% (average value was 6.5 × 10−6%). Post-processing of the eluate for further use in radiopharmaceutical synthesis was proposed. The post-processing procedure using a combination of Presep® PolyChelate and TK221 resins made it possible to obtain 44Sc-radioconjugates with high labeling yield (≥95%) while using small precursor amounts (5 nmol). The proposed method takes no more than 15 min and provides ≥90% yield relative to the 44Sc activity eluted from the generator. The labeling efficiency was demonstrated on the example of [44Sc]Sc-PSMA-617 and [44Sc]Sc-PSMA-I&T synthesis. Some superiority of PSMA-I&T over PSMA-617 in terms of 44Sc labeling efficiency was demonstrated (likely due to presence of DOTAGA chelator in the precursor structure). It was also shown that microwave heating of the reaction mixture considerably shortened the reaction time and improved radiolabeling yield and reproducibility of [44Sc]Sc-PSMA-617 and [44Sc]Sc-PSMA-I&T synthesis.
Purpose. To present results of the comparative analysis of the contribution of short-lived radioiodines to the thyroid radiation dose (TRD) in the population after two severe radiation accidents at nuclear reactors: the Chernobyl accident (1986) and the Fukushima accident (2011). Material and methods. The contribution of short-lived radioiodines to the TRD is expressed in fractions of the TRD from 131I (the main dose forming radionuclide). This contribution takes into account the ratio between doses from inhalation and ingestion intake of 131I, the ratios between dose factors of the expected dose to the thyroid gland in the case of inhalation and ingestion intake of iodine and tellurium isotopes, the ratios between time-integrated concentration of iodine and tellurium isotopes at the ground-level air and in foodstuffs (milk). Results. The typical contribution of short-lived radioiodines to TRD for the population accounts of few percent of dose to the thyroid gland from 131I following the Chernobyl accident as on March 15, 2011, the day of the main fallout after the Fukushima accident - within 15%. For both accidents the leading role among the short-lived radioiodines in terms of dose to the thyroid for the public belongs to 133I and 132I (due to the intake of 132Te and its radioactive decay to 132I in the body). Conclusion. Significant differences in estimates of the typical contribution of short-lived radioiodines to TRD for the population after two considered accidents can be explained by differences in the dominant pathways of the intake of radioiodine by population. The dominant pathway for the vast majority of the population in the contaminated areas following the Chernobyl accident was ingestion intake with locally produced cow’s milk. Following the Fukushima accident the dominant pathway was inhalation intake, because the Japanese authorities were able to quickly prevent the intake of radioiodine with foodstuffs.
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