S115
Brachytherapy - Physics
ESTRO 2026
designed for high-dose-rate (HDR) brachytherapy treatment of cervical cancer, allows a hybrid combination of interstitial and intracavitary catheters. Reconstruction of the channels corresponding to the semicircular ovoids using radiopaque fiducials or commercial MRI markers is not appropriate due to significant discrepancies between the actual source path and these reference markers in a curved applicator. For this reason, the manufacturer provides libraries of the applicator and its associated trajectories. However, verification of this data is relevant both at the initial reference of the applicator and during periodic quality control (QC). This study proposes two tools to improve the accuracy in verifying source positions in the applicators. Material/Methods:
Table. The mismatch between the measured positions of the radiation source and the “template” dwell-positions. Conclusion: 1. Measurements show that, when we are using the clinical “template” for “symmetrical” plans, the discrepancy between dwell-point measured and provided by “template” <1 mm, i.e. our results are in an agreement with data found previously [1].2. When employing the template for “asymmetrical” plans, the discrepancy for the first position is ~2 mm. For l others positions <1 mm, so we can apply it with acceptable accuracy under the condition of a 'smoothly loaded' applicator, as recommended. Keywords: commissioning of the applicator, detector array References: [1].I. Balode, V. Dmitrijeva, G. Boka, Z. Rudusa. PO- 2177 Study of dwell positions discrepancies from TPS in brachytherapy RING applicators. Radiotherapy and OncologyVol. 182 Supplement S1961–S1962, May, 2023 [2]. V.Stserbakov. PTW OCTAVIUS Detector 1600 SRS is virtuous tool in commissioning of brachytherapy applicator. - Radiotherapy and Oncology Vol.194 S327 (2024). Poster 263, ESTRO in Glasgow (2024). Digital Poster Highlight 439 Automation of the Verification of Dwell Positions in the Venezia Gynaecological Applicator Antonio Herreros 1,2 , Miquel Gubau-Besalú 3 , Eduard Agusti-Camprubi 4 , Gerard Trias 5 , Gislè Segura Roca 5 , Cristian Candela-Juan 1 1 Medical Physics Section – Radiation Oncology, Hospital Clínic Barcelona, Barcelona, Spain. 2 Fonaments Clínics, University of Barcelona, Barcelona, Spain. 3 Physics, University of Barcelona, Barcelona, Spain. 4 Radiation Protection, Hospital Clínic Barcelona, Barcelona, Spain. 5 Hospital Infrastructure and Biomedical Engineering, Hospital Clínic Barcelona, Barcelona, Spain
The developed tools are: Physical supports for semicircular ovoids: STL files generated from designs made using Autodesk Fusion 360 software for 3D printing of supports, such as the one shown in Figure 1, which secure the applicator ovoids and Ashland Gafchromic™ RTQA2 films, ensuring robust positioning during image acquisition and autoradiography. SPICA (Source Position Identification in Circular Applicators) image analysis program: A Python v3.10.11 script to analyze images obtained with radiochromic films, automating the identification of markers and radioactive source positions.The support design process included measurement collection, geometric design, prototyping using the mentioned design software, iterative optimization, and final production using an Ultimaker S3 printer. The radiochromic films were digitized using an EPSON 12000XL desktop scanner and analyzed using the SPICA script to identify markers and dwell positions of the source.
Purpose/Objective: The Venezia gynaecological applicator by Elekta,
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