Estimation of age-dependent internal dose from radiopharmaceuticals

Abstract

The age-dependence of the radiation dose absorbed in a target organ or the total body is determined by the mass, size, shape and separation of the organs as well as by the metabolic behaviour of the radionuclide compound. Using values of the specific absorbed dose for adults, the age-dependent effective dose equivalents for 28 radiopharmaceuticals (62 radionuclides) were calculated by modifying the above mentioned values, considering radiation type, organ mass and source-target separation. From the results, the currently used mathematical models for the modification of values of specific absorbed doses in the adult prove to be of sufficient accuracy. In comparison with the few available values calculated by Monte Carlo-techniques, our method overestimates the specific absorbed fractions by a factor of four in the least favourable case. For practical radionuclide dose estimates, these deviations are of minor importance as long as the availability of reliable information on the metabolic behaviour of radionuclide compounds and radiopharmaceuticals as a function of age is extremely limited. Considering, however, both the parenteral administration and the short half-life of radionuclides used in paediatric nuclear medicine, this uncertainty in regard to the gastrointestinal absorption and the biological half-lives is of little consequence for the results of absorbed dose calculations.

Dynamics of thyroid cancer incidence in Russia following the Chernobyl accident

“…As the risk of induction of radiogenic cancers at thyroid exposure to incorporated 131 I is strongly dependent on age at exposure and increases at young, age we study the quality of data on incidence for the age less than 30 years. As is shown in [12,14,15], for older age the thyroid dose is practically independent of age and determined by the amount of incorporated radionuclides only. The distribution functions for incidence ratios in this range and P values are presented in Figure 9 and Table 4.…”

“…In [12,14,15] the relation of thyroid dose D and unit activity of incorporated 131 I has been derived as a function of age at the time of the Chernobyl accident. It has been shown that the difference in absorbed doses of younger age groups can occur earlier than at the age of 20-24 years at exposure.…”

“…This applies equally to radiogenic thyroid cancer [1][2][3]. The above risk dependence will be better defined in case of thyroid exposure to incorporated 131 I, as in this case the thyroid exposure dose will depend on age at exposure [12,14,15]. So, induction of radiogenic cancers should change the shape of the age distribution of cancers.…”

An analysis of potassium iodide (KI) prophylaxis for the general public in the event of a nuclear accident

“…Effective half-life of radioiodide -The variability of the effective half-life of radioiodide is determined by the physical half-life of the isotope and its biological half-life (i.e., metabolic utilization and retention of organified iodide). Children and adolescents can be expected to exhibit higher turnover and elimination rates than adults (Rosenberg 1958;Heinrichs 1982;ICRP 1988). Dunning and Schwarz (1981) concluded that for adults, the observed range in biological halflives was from 21 to 372 days and for young children 4 to 39 days.…”

Prophylaxe strahleninduzierter Schilddrüsenkarzinome bei Kindern nach der Reaktorkatastrophe von Tschernobyl

“…Für Kinder im Alter von einem halben Jahr wird die Exposition mit 4000 mGy/MBq angegeben, für Ein-jährige mit 3400, für Fünfjährige mit 1900 und für zehnjährige mit 1200 mGy/ MBq. Bei Fünfzehnjährigen liegt die Dosis mit 800 mGy/MBq noch doppelt so hoch wie bei Erwachsenen mit 400 mGy/MBq (19,20,26).…”