ESTRO 2020 Abstract Book

S787 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.

Conclusion At the current technique stage, VMAT holds the dosimetric advantage in the single brain lesion SRS over IMPT. But IMPT could be used as an alternative approach when dose to the brain tissue exceeds constraints in VMAT plan. With the new technical development, SPArc showed its potential advantage to offer better dose sparing to the brain tissue over VMAT with an equivalent or higher CI in the peripheral brain lesion and deep centrally located lesion bigger than 4.74cc PO-1469 A new method for automated planning of prostate plans using geometrical ideal dose distribution M. Kusters 1 , M. Kentaro 2 , P. Van Kollenburg 1 , R.J. Smeenk 1 , R. Monshouwer 1 , Y. Nagata 2 1 Radboud university medical center, Radiation Oncology, Nijmegen, The Netherlands ; 2 Hirsohima University hospital, Radiation Oncology, Hiroshima, Japan Purpose or Objective Currently most of our radiotherapy plans are automatically generated with a single treatment technique template in the Auto-Planning module in Pinnacle 16.0.2 (Philips Healthcare, Fitchburg, WI, USA).

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.