ESTRO 2023 - Abstract Book

S1757

Digital Posters

ESTRO 2023

evaluated as non-robust under a classical proton treatment planning approach (Figure1). Both plans were robustly optimized using 3.5% range uncertainty and 2mm and 3mm setup uncertainty in head and neck areas respectively. Plan robustness were assessed with two methods. First, pre-treatment evaluation based on calculation of 28 perturbed scenarios of nominal plan, using a setup and range uncertainties of 2mm and 3%, respectively. Secondly, by recomputing the nominal plan on weekly CT scans acquired during the treatment course. The total delivered dose is estimated by deforming and accumulating the weekly evaluation doses to the planning CT.

Results The plan generation workflow is similar for IMPT and pArc with two major differences : weights required by pArc to achieve good targets coverage are significantly larger than for IMPT and pArc requires additional initial time for energies and spot selection algorithm. However, in the cases under study, the time for energy and spot selection is still below 2 minutes. Figure 2a-d show clinical goals evaluated for the two cases for pArc and IMPT. Error bars indicate the range of variation of every clinical goal evaluated over the set of perturbed scenarios on the planning CT. IMPT and pArc show similar range of variation. Clinical goals evaluated on the accumulated dose from the weekly CTs show that the deviations from the nominal plan are similar for both treatment techniques.

In general, for equivalent target coverage, doses at OARs are lower in pArc plans.