ESTRO 2023 - Abstract Book

S1839

Digital Posters

ESTRO 2023

Results So far, 305 clinical plans were simulated with the help of the PRIMO WatchDog scripts. The only manual intervention in the process (the export of DICOM files from the TPS) takes a few seconds per plan. Mean statistical uncertainties with k = 2 of (1.1 ± 0.3) % were obtained. Mean gamma passing rates for 3%/1 mm criteria was (98.3 ± 2.6) %. The scripts compiled as a Windows executable file, and also the source code, are available from the authors. Conclusion Python scripts were developed to automate the simulation setup for Monte Carlo simulations of clinical IMRT, VMAT and DCA plans with the PRIMO software, with a minimal workload for the medical physicist. This facilitates introducing PRIMO as a routine system for independent verifications. D. Lambisto Castro 1 , I. Romera-Martínez 1 , D. Jurado-Bruggeman 1 , S. Agramunt-Chaler 1 , A. Onsès-Segarra 1 , E. Massana- Melchor 1 , M. Vidal Borràs 2 , J. Vayreda Ribera 2 , A. Eraso-Urien 2,3 , C. Muñoz-Montplet 1,3 1 Institut Català d'Oncologia, Medical Physics and Radiological Protection, Girona, Spain; 2 Institut Català d'Oncologia, Radiation Oncology Department , Girona, Spain; 3 University of Girona, Department of Medical Sciences , Girona, Spain Purpose or Objective Irradiation of breast when internal mammary nodes are involved is dosimetrically challenging. The goal of this study is to compare the dosimetric outcomes of the irradiation of the breast using VMAT vs Hybrid techniques (combining static fields and modulated arcs) Materials and Methods Seventeen patients that underwent breast irradiation in our facility were studied. The irradiation at 2.67Gy per fraction during 15 days included: breast (PTV1), supraclavicular lymph nodes (PTV2), and internal mammary nodes (PTV3). For each patient, two dosimetric plans were generated: one using two VMAT half-arcs and one combining static fields with two half-arcs. For each PTV we obtained D98%, D2%, Dmean, and V95%, along with V20Gy and V5Gy for the homolateral lung. To check if the differences observed between both irradiation techniques are statistically significant, Wilcoxon-cox tests (p<0.01) were performed for each DVH parameter. Results Using hybrid techniques results in a statistically significant increase of the minimum dose (D98%) for all PTV’s, and a decrease in maximum dose (D2%) for all PTV’s (statistically significant for PTV1 and PTV2). No significant changes are found in Dmean between hybrid or VMAT techniques, but we observe a statistically significant increase in V95% for all PTV’s when using hybrid techniques. An increase in V20Gy and a decrease in V5Gy (both non-significant), are observed for the homolateral lung. No relevant data is shown for the contralateral lung because of the great statistical dispersion observed in our sample See table below for details. PO-2063 VMAT vs Hybrid techniques in breast irradiation with internal mammary nodes