ESTRO 2023 - Abstract Book

S1347

Digital Posters

ESTRO 2023

1 University of Medicine and Pharmacy and Medicine "Iuliu Hatieganu", Oncology Department, Cluj-Napoca, Romania; 2 Oncology Institute "Prof. Dr. Ion Chiricuta", Radiotherapy Department, Cluj-Napoca, Romania; 3 SIOP Europe – The European Society for Paediatric Oncology (SIOPE), QUARTET project, Brussels, Belgium; 4 The European Organisation for Research and Treatment of Cancer (EORTC) Headquarters, RTQA, Brussels, Belgium; 5 “Babes-Bolyai” University, Faculty of Physics, Cluj-Napoca, Romania; 6 University of Medicine and Pharmacy “Iuliu Hatieganu” , Department of Medical Informatics and Biostatistics, Cluj-Napoca, Romania; 7 “Babes-Bolyai” University, Faculty of Physics, Cluj-Napoca, Romania Purpose or Objective The management of primary brain tumors is challenging and complex, with several entities requiring irradiation. Acute toxicities can be dose-limiting and late effects, especially neuro-cognitive impairment, can be detrimental for patients. The ability to spare healthy tissue relies on a proper delineation of OARs. While manual contouring can largely vary between observers and is time consuming, especially with an increasing number of structures that require delineation, AI auto contouring could be a solution to simplify workflows, shorten planning times and harmonize practice. The aim of this study is to evaluate the accuracy of automatic segmentation for brain OARs and the impact of geometric variations on plan quality and dose distribution. Materials and Methods Thirty adult patients with primary brain tumors that underwent radiotherapy in a tertiary cancer center were randomly selected and retrospectively, manually recontoured. For each case, a second segmentation was performed using a first version of a deep-learning, guideline-based AI segmentation software (MVision GBAIS™). For 15 selected cases, VMAT plans were generated for each structure set (Manual_Plan/AI_Plan) using the same optimization criteria. For geometric comparison, Dice Similarity Coefficient (DSC), Average and 95% Hausdorff Distance (HD) were calculated. To assess the dosimetric impact, Gamma Analysis (3%/3mm,10% dose cut-off) and DVH comparison were performed,with Δ Dmean being the difference between AI_Dmean and Manual_Dmean for each OAR. For non-normal distributed data, a Wilcoxon signed ranks test was performed for paired data and correlations were assessed with the Spearman correlation coefficient( ρ ). Results Delineation of the 22 selected brain OARs was significantly faster using the automatic tool, with a median time of 1.13min for AI and 20min for manual (p<0.001). Median DSC and Average HD were 0.69(0.53-0.82) and 1.05mm(0.74-1.54). Median Average/95% HD were highest for MedullaOblongata(1.87/5.05mm) and lowest for Hippocampus_R(0.6/2.63). Highest DSC was found for Brain, Cerebellum and Brainstem (Median 0.96,0.92,0.98) and lowest for OpticTract_L/R, OpticNrv_L/R and OpticChiasm (Median 0.34/0.45, 0.48/0.53, 0.48). DSC was strongly correlated with the structure volume ( ρ =0.76, p<0.001), with a higher DSC for large OARs. The median gamma pass rate was 88.44% (85.57-90.83) (Figure1), with no correlation with the median DSC( ρ =0.03,p = 0.913). A significant correlation between Δ Dmean and DSC was only found in OpticNrv_L/R and OpticTract_L ( ρ 0.75/0.54 and 0.52, p<0.05)(Figure2).