ESTRO 2023 - Abstract Book

S1432

Digital Posters

ESTRO 2023

Agreement of mean PTV dose varied from -4% to 4% depending on case class for Mobius, see Fig 1. SciMoCa agreed with the TPS within +-2% for nine case classes and within +-1% for 17 case classes, except for 3 outliers. In the remaining two case classes, large deviations were seen for one patient in each class. For the breast case, the deviations were due to surgical clips in the target. For the stereotactic case being a brain tumor (Volume of GTV was 0.3ml), very small field s were used. Gamma 5%/3mm (the vendor recommendation for Mobius) resulted in pass rates > 85% across all case classes with the majority of patients > 95%. A similar result was found for SciMoCa for Gamma 2%/1mm. There was no correlation between modulation degree measures and outlier plans for SciMoCa, whereas Mobius struggled with high-modulation and stereotactic case classes. Investigation of SciMoCa outliers revealed differences in patient density definitions (bolus, immobilisation, air) and limitations of the TPS dose calculation. There was no pattern for Mobius outliers.