ESTRO 2023 - Abstract Book

S1826

Digital Posters

ESTRO 2023

time.

PO-2052 Impact of the VOLO Optimizer on Treatment Plan Quality of Stereotactic Prostate Radiotherapy.

T. Viren 1 , J. Seppälä 1

1 Kuopio University Hospital, Center of Oncology, Kuopio, Finland

Purpose or Objective VOLO-optimizer was developed to improve the performance and efficiency of previous Sequential optimizer (SO) on Cyberknife treatment planning. The aim of this study was to investigate the impact of the VOLO optimizer on the quality of stereotactic treatment plans of prostate cancer. Materials and Methods A total of 674 patients who received a stereotactic radiotherapy for prostate cancer between 2017 and 2022 were selected for the analysis. Treatment plans created before and after January 2021 were optimized using SO (n = 366, MultiPlan, Accuray, USA) and VOLO (n = 308, Precision, Accuray, USA), respectively. All the patients were treated in five fractions to total dose of 35 Gy or 36.25 Gy using Iris collimator. Before the analysis, the 35 Gy treatment plans were re-normalized to prescription dose of 36.25 Gy. Volume(cc), D95%(Gy) and D0.5cc(Gy) for PTV, mean dose, D0.5cc and D2cc for rectum and bladder, and Body mean dose were extracted from the data. Conformality index (CI) and dose gradient index (DGI) were calculated from the dose distributions. DGI was determined as a ratio of the volume of 50% the prescription dose to the volume of the prescription dose. CI was defined as the ratio of the prescription isodose volume to the PTV volume. An