To go further in the optimization of treatment planning in selective internal radiationtherapy (SIRT), radiobiological aspects can be accounted for with the OEDIPE software andused to design fractionation protocols. Dosimetry was performed using data from99mTc-MAAevaluations of 10 patients treated for hepatic metastases with SIRT. The maximalinjectable activity (MIA) was calculated, using a tolerance criterion onBEDmean,healthyliver equal to 54 Gy2.5, for different fractionationprotocols, varying the number of fractions, the repartition of activity and the time delaybetween fractions. OEDIPE was also used to calculate BEDmean and the EUD to the tumoralliver (TL) that would be delivered with those MIAs. Compared with a single-injectionprotocol, the MIA is increased on average by 23% ± 3%, 36% ± 5% and 45% ± 7% for fractionation protocols with 2, 3and 4 equal fractions, respectively, while BEDmean,TL is increased by 15% ± 2%, 23% ± 4% and 29% ± 5%. EUDTL, calculated for oneevaluation, is increased by 51%, 115% and 159% using 2, 3 and 4 equal fractions,respectively. For this evaluation, the optimal activity repartition for two-fractionprotocols is (3/4 − 1/4) fortime delays of less than 4 days, (2/3 − 1/3) for time delays between 4 and 6 days and (1/2 − 1/2) for time delays superior to 6 days.Finally, this study confirmed that OEDIPE can be regarded as a tool for treatment planningoptimization and fractionation protocol design in SIRT.

For targeted radionuclide therapies, treatment planning usually consists of theadministration of standard activities without accounting for the patient-specific activitydistribution, pharmacokinetics and dosimetry to organs at risk. The OEDIPE software is auser-friendly interface which has an automation level suitable for performing personalizedMonte Carlo 3D dosimetry for diagnostic and therapeutic radionuclide administrations. Meanabsorbed doses to regions of interest (ROIs), isodose curves superimposed on apersonalized anatomical model of the patient and dose-volume histograms can be extractedfrom the absorbed dose 3D distribution. Moreover, to account for the differences inradiosensitivity between tumoral and healthy tissues, additional functionalities have beenimplemented to calculate the 3D distribution of the biologically effective dose (BED),mean BEDs to ROIs, isoBED curves and BED-volume histograms along with the EquivalentUniform Biologically Effective Dose (EUD) to ROIs. Finally, optimization tools areavailable for treatment planning optimization using either the absorbed dose or BEDdistributions. These tools enable one to calculate the maximal injectable activity whichmeets tolerance criteria to organs at risk for a chosen fractionation protocol. This paperdescribes the functionalities available in the latest version of the OEDIPE software toperform personalized Monte Carlo dosimetry and treatment planning optimization in targetedradionuclide therapies.

Dans le cadre de l’amélioration des techniques d’étalonnage en anthroporadiamétrie, le Laboratoire d’Évaluation de la Dose Interne de l’IRSN a développé un outil numérique, « OEDIPE », pour modéliser la contamination interne dans des fantômes numériques voxélisés, simuler la mesure anthroporadiamétrique et estimer la dose interne. Si la précédente version d’OEDIPE permettait de bien modéliser des géométries de source comprenant un seul radionucléide localisé dans un organe particulier, elle était cependant limitée pour la modélisation d’une contamination formée d’un mélange de radionucléides dont la localisation évolue à partir de l’incorporation pour se distribuer dans plusieurs organes. Cet article a pour but de décrire les nouveaux modules développés pour permettre la définition de sources hétérogènes en composition et en répartition ainsi que l’importation automatique de distributions d’activité dérivées du calcul biocinétique. Ces nouveaux outils vont permettre d’étudier des cas de contamination plus complexes et l’influence de la biocinétique en mesure in vivo, afin de mieux estimer les coefficients d’étalonnage et les incertitudes correspondantes.