ESTRO 2025 - Abstract Book

S352

Brachytherapy - Physics

ESTRO 2025

Results: Calculated and measured results for the VH3 applicator (depth dose and profiles) are compared in Fig 2. An agreement within 5% between ACE and measurements was obtained for the depth dose curve (absolute units of Gy). Deviations of up to 25% in the penumbral region are due to the 2 mm diameter active volume of the detector being unable to resolve the steep dose gradients. Agreement for depth dose was worse (around 10%) for the VH2 applicator and will be investigated further using a second diamond detector. Conclusion: Applicator library models have been developed for Valencia applicators. Dose distribution have been calculated using the model-based dose algorithm of the TPS. Experimental verification was done by 3D scanning a 60Co calibrated microdiamond detector in a large water phantom. The 2 mm diameter of the detector cannot resolve the penumbral region, thus full commissioning of the applicators require additional film measurements. The worse agreement for the measured depth dose curve of the VH2 applicator could be due to the geometries sensitivity to the interior placement of the diamond active volume and warrants repeated measurements with a second diamond detector.

Keywords: Valencia applicator, ACE, measurements

References: 1) Ahnesjö A, van Veelen B and Carlsson Tedgren Å 2017 Collapsed Cone dose calculations for heterogeneous tissues in brachytherapy using Primary and Scatter Separation source data Comp. Meth. Progr. Biomed. 139 17-29 2)Kaveckyte V, Malusek A, Benmaklouf H, Alm Carlsson G and Carlsson Tedgren Å 2018 Suitability of a microdiamond detector to measure absorbed dose to water around 192Ir sources Med Phys. 44 429-437