Revised standardized dose estimates for radiopharmaceuticals

Objectives The OLINDA/EXM code developed by the RAdiation Dose Assessment Resource (RADAR) Task Group of the Society of Nuclear Medicine has been revised, incorporating realistic, NURBS-type models based on the recent standardized masses defined by the ICRP in its publication 89 (including several new organs), and a new model of the gastrointestinal (GI) tract. Data from biokinetic models from various publications of the ICRP Task Group on Radiopharmaceutical Dosimetry were entered into the code and new standardized dose estimate tables were developed.

Methods ICRP Publications 53, 80, and 106 contain detailed and up-to-date biokinetic models for many radiopharmaceuticals in common use. Dozens of the most popular compounds were selected, and the most current values recommended by the ICRP Task Group were used as input data in OLINDA/EXM. Dose estimates for adults and pediatric subjects of 5 standard ages, as well as for pregnant women at 3 stages of gestation (using the established data of Russell et al.) were generated and tabulated. Direct comparisons to existing dose estimates, using the traditional, stylized models, were also tabulated. Effective doses using the recent (ICRP 103) tissue weighting factors were also calculated and compared to previous values (ICRP 30 and 60).

Results Numerical results for the individual organ doses and effective doses are not significantly different from those based on the previous generation of phantoms. Doses for eyes, esophagus, salivary glands and prostate gland are now provided, so a more complete treatment of effective dose is possible. Understanding of doses to the new GI tract model, as defined by the ICRP, changes somewhat, but the doses to the individual segments are generally similar to those in the old definition.

Conclusions The new generation of models now available in the OLINDA/EXM code permits a recalculation of standardized dose estimates with more complete and anatomically accurate anthropomorphic models