Published online by Cambridge University Press: 30 September 2014
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.