Age-dependent thyroid absorbed doses for radiobiologically significant radioisotopes of iodine.

摘要: In light of the post-Chernobyl increase in pediatric thyroid cancer incidence, among other recent events, there is renewed interest radioiodine dosimetry and effects. Among radioiodines produced fission 235 U, only 131 I [(T 1/2 ) p =8.04 d], 132 (2.3 h), 133 (20.3 135 (6.7 h) may undergo significant environmental dispersion. Age-dependent absorbed dose estimates for these radiobiologically medical radioisotopes 123 (13.2 125 (60 d) have been derived, incorporating effect absorption following inhalation or ingestion. This has generally ignored previously derived doses to thyroid. Based on latest ICRP lung gut models, inhaled at a rate 0.175 h -1 exhaled 0.101 0.118 (depending age) ingested completely stomach 1 . Whole-body compartmental models (SAAM II) were fit published 24-h uptakes, half-times, 48-h plasma concentration protein-bound iodine. The resulting fitted used calculate residence times radioiodine. mean [cGy/37 kBq (rad/μCi) injected intravenously] then calculated using age-dependent S(thyroid←thyroid) factors (MIRDOSE III), with highest (from 0.49 36 I) newborns lowest 0.014 1.4 adults inverse relation mass. Although substantially (30 70%) less than that injection all ages, it markedly (25%) ingestion short-lived I.