ESTRO 2020 Abstract book

S837 ESTRO 2020

However, this approach does not always automatically lead to the best plan solution and additional manual optimization steps are needed. In this study we investigated a new inhouse-developed application (see reference 1) that calculates the geometrical ideal dose distribution (GIDD), which can be used for a priori estimation of the best possible organs at risk (OARs) sparing. We validated this GIDD application for volumetric arc therapy (VMAT) prostate using an automated personalized planning approach. Material and Methods The GIDD application calculates an geometrically ideal dose distribution that takes the geometric beam setup and delineated contours of the PTV into account, as well as body and OARs. The benefit of this approach is that this application can predict dose distributions which mimic clinical feasible Pareto optimal plans. The predicted dose volume histograms (DVHs) for the OARs were used to individualize the objectives values for the current template technique to acquire the automated dose optimization in a personalized manner for VMAT prostate planning. Data of 10 automatically planned clinical prostate patient plans were used to compare the single template technique with the geometrical ideal dose approach. In all these plans two VMAT arcs were used (95 to 265 o ) CW and CCW, by which 70 Gy is given in 28 fractions of 2.5 Gy. Plan quality of the clinical plan and personalized plan were compared by dose metrics comparison for the OARs. Results Overall, plan quality was improved for the 10 prostate cases. Figure 1 shows an example of the dose distribution and DVHs between original auto-planning approach and new personalized automated planning approach.

Table 1: Differences in mean dose, percentages for 30 Gy and 60 Gy volumes for rectal wall, anal wall and bladder and monitor units (MUs). Positive values indicate that these dose metric values were improved compared to the clinical plan. The average mean dose to the rectal wall and bladder were improved with 2.8 and 2.0 Gy, respectively. The average V30 and V60 for the rectal wall was improved with 3.4% and 0.8%, respectively. The other dose metrics did not significantly improve. The MUs were slightly higher and were on average 728 MUs. Conclusion We showed that this GIDD application can be used to improve the plan quality by using a personalized template technique for VMAT prostate cases. The application is independent of the TPS applied and can be used for all different sites. Reference 1. Kentaro et al. Medica 2019 57:115-122. PO-1470 Personalized Planning for prostate radiotherapy in Pinnacle Evolution improves planning efficiency M. Kusters 1 , L. Bouwmans 2 , K. Bzdusek 2 , P. Van Kollenburg 1 , L. Abbenhuis 1 , R.J. Smeenk 1 , R. Monshouwer 1 1 Radboud university medical center, Radiation Oncology, Nijmegen, The Netherlands ; 2 Philips Healthcare, Radiation Oncology Solutions, Fitchburg, USA Purpose or Objective In this study we compare our current automated planning approach for volumetric art therapy (VMAT) prostate radiotherapy plans, using a single treatment technique template in the Auto-Planning module in Pinnacle 16.0.2 (Philips Healthcare, Fitchburg, WI, USA), with automated planning algorithms in Personalized Planning in Pinnacle Evolution. We investigate the plan quality and planning efficiency of Data of 10 automatically generated clinical prostate patient dose-plans were used to compare the single template technique with the personalized template optimization. In all these plans two VMAT arcs were used (95 to 265 o ) CW and CCW, to deliver 70 Gy in 28 fractions of 2.5 Gy. For the current single template technique for the Auto-Planning module objectives for organs at risk (OARs) that are dictated by the clinical goals were used. In Pinnacle Evolution a personalized template can be made the plans in this study. Material and Methods

Figure 1 shows the axial dose distribution and DVHs between original auto-planning (solid line) and personalized automated planning (dashed lines) approach. Table 1 shows the results of OARs sparing and MUs difference.