IDAC-Dose 2.2, an internal dosimetry software for diagnostic nuclear medicine based on the latest ICRP adult and paediatric reference computational phantoms.

Abstract

Background: For patients investigated with radiopharmaceuticals, it is important to be able to perform valid calculations of the absorbed dose in organs and tissues. An internal dosimetry computer program, IDAC-Dose2.1, has been updated to be based on the ICRP specific absorbed fractions and computational framework of internal dose assessment for 12 adult and paediatric reference individuals given in ICRP Publication 133 and 155. The updated dosimetry software intended for nuclear medicine is named IDAC-Dose2.2. The calculations are based on radionuclide decay scheme of ICRP Publication 107. Biokinetic models can be based on up to 83 different source regions irradiating 48 target tissues, defining the effective dose as presented in ICRP Publications 60 and 103. The computer program was validated against another ICRP dosimetry software, DCAL ver. 2022, that employs the same computational framework and is used for occupational and environmental intakes of radionuclides. IDAC-Dose2.2 calculates absorbed doses to the 2 adult and 10 paediatric,15-yrs, 10-yrs, 5-yrs, 1-yr, 100 days (infant) and 0 day (new-born), sex specific ICRP reference phantoms. It has an additional sub-module which can interpolate the calculated absorbed dose and effective dose to an arbitrary age between 0 and 20 years (20 years = adult) or an arbitrary weight of 3.5-73 kg for male and 3.5-64 kg for female instead of only using the 6 fixed phantoms ages.

Results: IDAC-Dose2.2 was applied on three frequently used radiopharmaceuticals: intravenously administered 2-[¹⁸F]FDG, orally administered ^99mTc-pertechnetate and ¹³¹I-iodide. Using the tissue weighting factors from ICRP Publication 103, the effective dose per administered activity was estimated for 2-[¹⁸F]FDG: 0.017mSv/MBq, 0.020 mSv/MBq, 0.029 mSv/MBq, 0.044 mSv/MBq, 0.075 mSv/MBq, 0.16 mSv/MBq 0.16 mSv/MBq for adult, 15-, 10-, 5-, 1-year old, 100 days (infant) and 0 day (newborn), respectively. Effective dose of 0.034 mSv/MBq was also calculated for 2-[¹⁸F]FDG to a reference person of 8-years old. For the same three radiopharmaceuticals, S-values were generated for all phantoms in IDAC-Dose2.2 and validated against the dosimetry program DCAL, showing identical results.

Conclusions: The internal dosimetry program IDAC-Dose was updated to include all 12 specific sets of absorbed fractions of the ICRP adult and paediatric reference phantoms and applied to three radiopharmaceuticals for validation against DCAL and to generate improved absorbed dose estimations for preadults in diagnostic nuclear medicine. The sub-module for age or weight interpolation of absorbed doses follows the ICRP computational framework used for members of the public. IDAC-Dose2.2 will used by the ICRP for absorbed and effective dose calculations in diagnostic nuclear medicine. The results from other software, which uses the same primer data (e.g. ICRP SAF values or decay data) could deviate from those of IDAC-Dose 2.2 and published ICRP dose values if the software do not follow the ICRP computational framework for internal dosimetry. IDAC-Dose2.2 is a free software for research and available at http://www.idac-dose.org . The online version can be operated directly through a web browser and the standalone version is an executable file, which is downloaded and installed directly on the local computer.