S1813
Physics - Dose prediction/calculation, optimisation and applications for photon and electron planning
ESTRO 2026
Palanivel Duraikannu 1,5 , Boopalan Balaji 6 , Karthick Nagamuthu 7 1 Division of Physical Sciences, Karunya Institute of Technology and Sciences (Deemed University),, Coimbatore, Tamilnadu, India. 2 Department of Radiation Oncology, Yashoda Super Speciality Hospital and Cancer Institute, Ghaziabad, India. 3 Department of Radiation Oncology, Fortis Hospital, Mohali, India. 4 Department of Radiation Oncology, Kovai Medical Center and Hospital, Coimbatore, India. 5 Department of Radiation Oncology, Manipal Hospital, Bangalore, India. 6 Department of Radiation Oncology, J. N. Medical College, KLE Academy of Higher Education and Research (Deemed to be University),, Belagavi, Karnataka, India. 7 Department of Radiotherapy, United Lincolnshire Teaching Hospitals NHS Trust Lincoln,, LN25QY, United Kingdom Purpose/Objective: This study aimed to evaluate and compare the dosimetric performance and treatment delivery efficiency of the Anisotropic Analytical Algorithm (AAA) and the Acuros XB (AXB) algorithm in dose-to-medium (Dm) and dose-to-water (Dw) reporting modes for volumetric-modulated arc therapy (VMAT) in head- and-neck cancer patients treated on the Halcyon platform. Material/Methods: A retrospective cohort of 25 patients with advanced head-and-neck squamous cell carcinoma (HNSCC) treated between 2024 and 2025 was analyzed. All patients underwent immobilization with a five-clamp mask, CT simulation with 3 mm slice thickness, and contouring of target volumes and organs-at-risk (OARs) per institutional protocols. Clinical VMAT plans were initially generated in Eclipse v15.6 using AAA, then recalculated with AXB in both Dm and Dw reporting modes, keeping identical arc geometry and optimization parameters. Dosimetric endpoints for PTVs (D98%, D95%, D2%, mean dose, conformity index, and homogeneity index) and OARs (Dmax and Dmean for critical structures) were compared. Treatment efficiency was assessed using monitor units (MU), modulation factor, and beam-on time (BOT). Pretreatment quality assurance (QA) was performed using portal dosimetry with TG-218 criteria. Results: AXB-Dm and AXB-Dw both yielded slightly reduced PTV_high coverage compared with AAA, with significant decreases in D98% and D95% (p < 0.05), while mean dose differences were negligible. OAR doses were generally comparable, though AXB-Dm reported a lower mean mandible dose and slightly higher spinal cord Dmax. Treatment delivery efficiency was notably impacted in AXB-Dm plans, which required 20% more MUs, higher modulation factors,
integrates PenRed's capabilities into the Python ecosystem, both utilities can be executed as Python functions, simplifying their use. These utilities eliminate the need to create complex geometry or configuration files, as all necessary parameters can be passed as function arguments.Users can vary parameters such as the anode composition and angle, source position, focal spot size, filter's compositions and widths, among others. A complete description of all parameters is available in the dedicated X-ray pyPenred documentation (https://penred.github.io/PenRed/pyPenred/simulation .xray.html). Results: The results from both utilities have been validated against reference X-ray spectra generated using tools like G4XRTube (based on Geant4) and other established models. Several case studies with varying parameters were conducted. The results from one such example are shown in Figure 1, confirming good agreement with the references.
Figure 1 X-ray tube configuration and the corresponding validation Conclusion:
The primary benefit of the developed tools is their ability to characterize an X-ray beam accurately without requiring in-depth knowledge of the underlying physical parameters or complex configuration procedures, thereby facilitating their application across various fields. References: V. Giménez-Alventosa, V. Giménez Gómez, S. Oliver, PenRed: Anextensible and parallel Monte-Carlo framework for radiation transportbased on PENELOPE, Computer Physics Communications 267 (2021)108065. doi:https://doi.org/10.1016/j.cpc.2021.108065 Keywords: x-ray, penred, monte carlo Digital Poster 922 Evaluation of Dose-to-Medium and Dose-to-Water Reporting Modes of Acuros XB Algorithm Compared with AAA in Head-and-Neck VMAT in Halcyon Ring gantry. VENUGOPAL SUNDARAM 1,2 , Khanna David 1 , Mohandass Palanisamy 3,1 , Rekha Arya 2 , Nilotpal Chakravarty 2 , Pavithra Palanisamy 2 , Anto Vaz S 1,4 ,
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