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Brachytherapy - Physics
ESTRO 2026
in a clinical HDR brachytherapy setting for prostate cancer. Radiotherapy and Oncology. 2024 Nov 1;200:110501.[3] Dürrbeck C, et al. Influence and compensation of patient motion in electromagnetic tracking based quality assurance in interstitial brachytherapy of the breast. Medical Physics. 2022 Apr;49(4):2652-62.
with controlled implant displacements (range: 1–20 mm). The difference between measured and applied implant displacement was calculated. Results: The most stable position relative to the prostate was identified 35 mm distal to the Foley balloon (Figure 1), supporting the use of an internal reference sensor at this location.
Digital Poster 1869
Suggestion for a standardized determination of beam quality correction factors for experimental dosimetry in Brachytherapy Frank W. Hensley 1 , Thomas Failing 2,3 , Günther H. Hartmann 4 , Thorsten Schneider 5 , Klemens Zink 2,6 1 Dept. of Radiation Oncology (retired), Heidelberg University Hospital, Heidelberg, Germany. 2 Institute of Medical Physics and Radiation Protection (IMPS), TH Mittelhessen University of Applied Sciences, Giessen, Germany. 3 Radiotherapy North, Center for Radiotherapy and Radiooncology, Westerstede, Germany. 4 Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany. 5 Dept. 6.3 Radiation Protection Dosimetry, Physikalisch-Technische Bundesanstalt (PTB), Braunschweig, Germany. 6 LOEWE Research Cluster for Advanced Medical Physics in Imaging and Therapy (ADMIT), TH Mittelhessen University of Applied Sciences, Giessen, Germany Purpose/Objective: Absorbed dose is only infrequently measured in radiation fields for brachytherapy (BT). Reasons are the geometrical uncertainties involved in the positioning of source and detector, and particularly missing recommendations in form of Codes of Practice (COPs). Although the probe method as defined in TRS 398[1] is in principle also valid for BT, existing COPs recommend no beam quality correction factors kQBT,Q0 for specific detectors or brachytherapy qualities correcting for different detector response under calibration conditions in comparison to a measurement. In BT, measuring conditions differ due to different radiation spectra and the highly inhomogeneous radiation field. The steep divergent fluence gradient near a radiation source causes different volume averaging in a detector in different positions and orientations.
Phantom experiments demonstrated that motion- corrected EMT achieved maximum Euclidean errors of 0.46 mm across periodic translations (Figure 2.b). For implant displacement, the maximum difference between applied and measured shifts was 1.5 mm (Figure 2.c).
Conclusion: A Foley-catheter-based reference sensor extends EMT from QA of implant geometry to localization of the implant position relative to prostate anatomy, while compensating for motion-induced distortions during acquisition. Keywords: Electromagnetic tracking, QA, prostate References: [1] Bert C, et al. Electromagnetic tracking for treatment verification in interstitial brachytherapy. Journal of contemporary brachytherapy. 2016 Oct 1;8(5):448- 53.[2] Androulakis I, et al. Assessment of integrated electromagnetic tracking for dwell position monitoring
Most determinations of kQBT,Q0 are limited to single measuring positions and orientations[2], providing
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