S2352
Physics - Quality assurance and auditing
ESTRO 2026
head and pelvis protocols, with two consecutive measurements (I and II in the tables) per protocol taken one month apart to evaluate stability. Parameters analyzed included geometric accuracy, high- and low-contrast resolution, image uniformity, and Hounsfield unit (HU) constancy. All datasets were processed using both Pylinac and Smári software. Results: Results are presented in tables 1 and 2. Both tables contain values generated by Smári and Pylinac for two measurement series. Initial values at acceptance, measured using manual method, are shown as well. The comparison between Pylinac and Smári demonstrated high consistency across all tested image quality parameters. Minor numerical discrepancies were observed, particularly in HU uniformity for the head protocol, but without clinical significance. Both software tools confirmed compliance with national QC tolerances for all parameters except uniformity in the head protocol, which remained within acceptable stability limits. Geometric distortion, MTF-based spatial resolution, and low-contrast detectability showed excellent agreement. The results confirmed that Pylinac analysis is objective, reproducible, and sufficiently accurate for routine image quality assurance.
Figure 1 – Boxplot of Δ D and GPR Conclusion:
We demonstrate a fast, simple PSQA method for CBCT-based sCT suitable for pelvic oART. The approach reliably identifies errors in synthetic CT generation, and future work will explore applications to other anatomical sites. References: [1] Nella F, Tanadini - Lang S, Dal Bello R. Clinical implementation of patient - specific quality assurance for synthetic computed tomography.Phys ImgRadiat Oncol. 2025 Apr 4;34: 100764. Keywords: synthetic CT, oART, PSQA Digital Poster 1626 Validation of the Pylinac Catphan Module for CBCT QA for Clinical Use Milos Kopunovic 1 , Borislava Petrovic 2,3 , Katarina Bito 1,4 , Veljko Petrovic 1 , Milos Jonic 1 , Jelena Stankovic 1 , Dragan Nikolic 1 1 Radiotherapy departement, University clinical center Nis, Nis, Serbia. 2 Radiotherapy departement, Oncology institute Vojvodina, Sremska Kamenica, Serbia. 3 Faculty of sciences, University of Novi Sad, Novi Sad, Serbia. 4 Faculty of electronic engineering, University of Nis, Nis, Serbia Purpose/Objective: The aim of this study was to validate Pylinac, a free open-source software tool that can be used for cone- beam computed tomography (CBCT) image quality assessment in radiotherapy. The evaluation was conducted through a comparison with Smári, the official web-based analysis platform developed for Catphan phantoms. The primary objective was to determine whether Pylinac can provide clinically acceptable, sustainable and reproducible results for CBCT quality assurance (QA) in routine practice Material/Methods: Image quality measurements were performed on the Varian XI CBCT system integrated into a VitalBeam linear accelerator at the University Clinical Center Nis, Serbia. The Catphan 604 phantom was scanned using
Conclusion: The Pylinac CBCT analysis module demonstrated results comparable to the official Smári software, validating its reliability for clinical implementation. Given its open-source nature, accessibility, transparency, and reproducibility, Pylinac represents a cost-free alternative for routine CBCT QC in radiotherapy. The findings support its use for ensuring consistency of image quality over time. References: 1. Klein E.E. et al. Task Group 142 Report: QA of Medical Accelerators. Med. Phys. 36, 2009.2. EFOMP– ESTRO–IAEA. Quality Control in Cone Beam Computed Tomography (CBCT), 2019.3. Fernandes L.C. et al. Evaluation of Various Free Software Options for Catphan 504 Phantom. Braz. J. Radiat. Sci., 2024.4. Catphan® 604 Manual. The Phantom
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