ESTRO 2025 - Abstract Book

S171

Brachytherapy -Breast

ESTRO 2025

3093

Proffered Paper Implant-based patient identification using electromagnetic tracking: A novel, automated solution to prevent patient mix-ups in breast brachytherapy Christopher Dürrbeck 1,2 , Rainer Fietkau 1,2 , Vratislav Strnad 1,2 , Christoph Bert 1,2 1 Department of Radiation Oncology, Universitätsklinikum Erlangen, Erlangen, Germany. 2 Comprehensive Cancer Center, Universitätsklinikum Erlangen, Erlangen, Germany Purpose/Objective: Patient or treatment plan mix-ups are the most serious patient-specific human errors in brachytherapy and can have potentially drastic consequences. Despite the severity of such treatment errors, many brachytherapy departments rely only on review by a second, independent person, which does not eliminate the risk of human failure. Automated solutions for patient identification are not widely used. In this work, we developed and retrospectively evaluated an automated patient identification method based solely on the geometry of the interstitial implant in breast cancer patients. Material/Methods: The implant geometry is assessed using an electromagnetic tracking (EMT) system that provides real-time positional data of each catheter with sub-millimetre accuracy. The EMT sensor is attached to the check cable of a prototype afterloader (Elekta Brachytherapy, Veenendaal, Netherlands), allowing seamless integration of implant geometry data acquisition into the mandatory check cable run prior to each fraction [1]. The measured implant geometry is rigidly registered to the CT-based implant geometry associated with the clinical treatment plan and quantitatively compared using a similarity metric based on a distance-to-agreement (DTA) criterion (2-12 mm) and a pass rate threshold (95%). The implants of 75 patients who received brachytherapy either as APBI or boost after WBI were compared, resulting in 5625 patient-treatment plan combinations. To simulate the clinical error scenario where a treatment plan is accidentally loaded that contains fewer catheters than the actual implant, only this number of catheters was considered in the implant comparison. Results: In all cases, the same-patient similarity score was highest for all distance thresholds considered. Applying a universal DTA criterion of 6 mm allowed identification with 99.7% accuracy, 72.4% sensitivity, and 0% false positive rate. Refining the universal DTA classifier with a catheter-wise criterion further improved the performance to 100% accuracy, 95.3% sensitivity, and 0% false positive rate. Conclusion: Interstitial implants in breast brachytherapy are virtually unique, so determining their geometry prior to each fraction is a viable option for patient identification. The EMT-based automated technique has proven to be effective in detecting patient or treatment plan mix-ups. When implemented into the mandatory check cable run, it enhances patient safety without compromising workflow efficiency. This demonstrates another beneficial use case for EMT in brachytherapy, alongside accurate applicator reconstruction, improved needle navigation and placement, and advanced pre-treatment verification.

Keywords: treatment verification, treatment errors

References: [1] Kallis K, Kreppner S, Lotter M, Fietkau R, Strnad V, Bert C. Introduction of a hybrid treatment delivery system used for quality assurance in multi-catheter interstitial brachytherapy. Phys Med Biol. 2018 May 2;63(9):095008. doi: 10.1088/1361-6560/aabb5a. PMID: 29616659.