S114
Brachytherapy - Physics
ESTRO 2026
("asymmetric"), when the applicator source channel tip is free of loading. Material/Methods: The method is well suited for studying such fine effects is the technique using PTW OCTAVIUS 1600 SRS 2D-dimensional array [2]. Plastic Applicator Ring 60ºd26 (Bravos, Varian) applicator is taken as an example. The applicator was fixed on central part of 2D-dimensional array. Time of collecting charge is ~7 s /dwell-position. Step is 5 mm. Measured files were imported and processed in Excel.
Conclusion: This survey highlights a clear mismatch between the very limited access to HDR-BT audits in Europe and the strong consensus on their necessity. In addition, users provided their opinions on the aspects that such audits should cover, offering guidance for future design. Stronger recommendations from organizations and professional societies are required to expand audit infrastructures and make them a standard component of quality assurance in HDR BT. Keywords: HDR BT audits, dosimetry audits, Quality assurance Approving of Ring Applicator (Varian) template for clinical use by means of OCTAVIUS (PTW) 2D-array Vladimir Stserbakov 1 , Alina Griva 2 , Inga Balode 2 , Galina Boka 2 1 Radiotherapy, North-Estonia Medical Center Foundation, Tallinn, Estonia. 2 Department of Clinical Medical Physics and Dosimetry, Riga East University Hospital, Riga, Latvia Purpose/Objective: Carry out commissioning of the RING applicator for standard and non-standard clinical cases for BRAVOS. To consider the RING applicator in both interesting cases of exposure dwell-loading positions: for standard ("symmetric", i.e. uniformly loading of left and right side of applicator) and for non-standard Digital Poster 356
Figure.A – Measured coordinates of the dwell- positions. B – Drawing of the correspondence between
the measured and “template” dwell-positions positions. C – View of library dwell-positions
(equidistant)The library dwell-positions (equidistant) from the treatment planning system cannot be used for treatment planning because of the mismatch with the measured (film) data. These library dwell-positions should be corrected into some “template” dwell- positions for father use in clinic treatment.It was investigated three loading clinical cases of “template” (Fig. A):Standard ("symmetric"), i.e. Meas1Long.Non- standard ("asymmetric"), when the applicator source channel tip (2 cm) is free of loading (Meas2Middle),Non-standard ("asymmetric"), when the applicator source channel tip (4 cm) is free of loading (Meas3Middle).Finally, the matching was analyzed (Table). Results: Measurement Meas2Long (=M1) – the entire length of the applicator is loaded with dwell positions with dwell time of 30 s (“symmetric”). Measurement Meas2Middle (=M2) – when 2 cm of the applicator tip are loaded with dwell time = 0 s (“asymmetric”). Measurement Meas3Short (=M3) – when 4 cm of the applicator tip are loaded with dwell time = 0 s (“asymmetric”). Cases M2 and M2 represent “asymmetric” gynecological plans.
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