Assessment of absorbed dose for Zr-89, Sm-153 and Lu-177 medical radioisotopes: IDAC-Dose2.1 and OLINDA experience.

OBJECTIVE: In this article, IDAC-Dose2.1 and OLINDA computer codes are compared as they are the most widely used software tools for internal dosimetry assessment at the present time. OLINDA/EXM personal computer code was created as a replacement for the widely used MIRDOSE3.1 code. IDAC-Dose2.1 was developed based on the ICRP specific absorbed fractions and computational framework of internal dose assessment given for reference adults in ICRP Publication 133. IDAC uses cumulated activities per administered activity in hours and calculates the absorbed dose and the effective dose. The program calculates the dose in the Eckerman stylized family phantoms. It is useful in standardizing and automating internal dose calculations, assessing doses in clinical trials with radiopharmaceuticals, making theoretic calculations for existing pharmaceuticals, teaching, and other purposes. METHODS: To produce such a comparison, the results of this work were compared with available published data in the literature on radiopharmaceuticals. Radiopharmaceuticals with 89Zr, 153Sm, 177Lu radionuclides are used as the basis for the comparison. 89Zr, 153Sm, 177Lu radionuclides are regarded as the future of radiopharmaceutical treatment. For 89Zr, two different labelled carriers, Zr-89_cMAb U36 and Zr-89 Panitumumab, were used on patients. RESULTS: The results show a clear difference in terms of absorbed dose of the Zr-89 radiopharmaceuticals for red bone marrow when calculated by IDAC-Dose2.1 (0.76 mGy/MBq), while the estimated absorbed dose in literature results is 0.07 mGy/MBq and 0.14 mGy/MBq when the calculation is done by OLINDA program. In the case of 177Lu-EDTMP, the absorbed dose in red bone marrow is in reasonable agreement (0.63 mGy/MBq and 0.8 mGy/MBq for IDAC-Dose2.1 and OLINDA, respectively). A significant difference was found for the absorbed dose in the bone surface, which was almost twice as high for OLINDA (2.1 mGy/MBq for IDAC-Dose2.1 and 5.4 mGy/MBq for OLINDA). In some direct cases, the calculated absorbed dose in the urinary bladder wall with OLINDA is ten times higher compared to WinAct (which was utilized to calculate the total activity in the organs and tissues) and IDAC 2.1. These results are considered key to greater accuracy in internal dose calculation.

Comparative study on application of177Lu-labeled rituximab, tetulomab, cetuximab and huA33 monoclonal antibodies to targeted radionuclide therapy.

PurposeDose coefficients from rituximab, tetulomab, cetuximab, and huA33 monoclonal antibodies labelled with the radionuclide177Lu were estimated for human organs and tumours via a theoretical simulation based on experimental results.MethodsThe real experimental results were obtained from radiopharmaceutical distribution in hairless mice. Using the Sparks and Aydogan method, the cumulated activity for humans was recalculated. The simulation was used to assess the behaviour of MAbs labelled with177Lu after injection into the human body. The average absorbed doses were calculated for the most exposed organs and tissues.ResultsThe huA33 monoclonal antibodies (MAbs) labelled with 177Lu (Lu-rituximab, Lu-tetulomab, Lu-cetuximab, and Lu-huA33), presented the maximum nuclear transformation per Bq intake for the main organs (blood, kidneys, liver, lung, and spleen, as well as for a tumour) The absorbed dose in the liver is three times lower for Lu-huA33 compared to the other drugs. In the case of cetuximab, the spleen received the lowest dose compared to the other drugs. The dependencies on absorbed dose for the alveolar, bronchioles, bone surface, heart wall, kidneys, liver, lung, lymphatic nodes, and spleen, are presented. For tumours, the absorbed dose for each drug is calculated separately for a sphere of unit volume by using the information on the injected dose.Conclusion, The ratios of the dose coefficient for the tumour to each organ, indicate that lutetium-177 can be recommended for targeted radionuclide therapy since the dose per tumour is much greater than the dose per organ.