OLINDA/EXM 2.0: The new generation dosimetry modeling code

Objectives The OLINDA/EXM code developed by the RAdiation Dose Assessment Resource (RADAR) Task Group of the Society of Nuclear Medicine has standardized dose calculations for diagnostic and therapeutic radiopharmaceuticals. The previous generation of anthropomorphic phantoms were based on the Oak Ridge models, which employed geometrical shapes to define the body and its organs. These models have been replaced with realistic, NURBS-type models based on the recent standardized masses defined by the ICRP in its publication 89. These and other new models have been implemented in a new version of the OLINDA/EXM code.

Methods The realistic adult, pediatric, and pregnant female phantom series were used in Monte Carlo simulations to produce organ specific absorbed fractions (SAFs). These values were used with recently released decay data to produce organ dose factors (DFs), which are used by the code. Updated techniques and data for modeling the kinetics of the gastrointestinal tract, gender averaging of dose, and calculation of effective dose were also implemented in the code. The code remains in the Java environment, although its structure was reorganized. The ability to automatically combine results for multiple nuclides (e.g. from a decay series) was added.

Results The code remains user-friendly and easy to use. Numerical results are not significantly different from those based on the previous generation of phantoms, although some adjustments in understanding of doses to the GI tract, as proposed by the ICRP, will be needed. The ability to calculate doses to eyes, esophagus, salivary glands, and the prostate gland, and implementation of the new effective dose weighting factors represent a significant advance. Previous phantoms and effective dose weighting factors were retained for comparisons.

Conclusions The new generation of models is now available in the OLINDA/EXM code, and represents a significant improvement in standardized dose calculations