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Session: Brachytherapy - I [Return to Session]

Automation of Implant Reconstruction in Interstitial Brachytherapy of the Breast Using Electromagnetic Tracking

C Duerrbeck*, R Fietkau, V Strnad, C Bert, Universitatsklinikum Erlangen, Erlangen, DE


SU-H300-IePD-F7-4 (Sunday, 7/10/2022) 3:00 PM - 3:30 PM [Eastern Time (GMT-4)]

Exhibit Hall | Forum 7

Purpose: The purpose of this study was to develop a technique to automate the reconstruction of catheter implants in interstitial brachytherapy (iBT) of the breast by means of electromagnetic tracking (EMT) with the goal of making treatment planning as time-effective and accurate as possible.

Methods: The catheter implants of 20 patients were assessed using an afterloader prototype (Flexitron, Elekta Brachytherapy, Veenendaal, The Netherlands) equipped with an EMT sensor (Aurora, NDI, Waterloo, Canada). Data were acquired immediately after the planning CT with the patient still in scan position and rigidly registered to the CT image space using the catheter fixation buttons as landmarks. In order to further improve the reconstruction accuracy, EMT reconstruction points were taken as starting points to define small regions of interest (ROI) around them in the CT image. Within these ROIs, standard image processing operations including thresholding and blob detection were used to segment the catheter trace, thus refining the reconstruction. The perpendicular distance between the refined EMT implant reconstruction points and the manual catheter reconstruction by an experienced treatment planner was calculated as a measure of their geometric agreement.

Results: The acquisition time of the EMT system is 22 s per catheter and 6-11 min for the entire implant, the time for refinement is <5 min. The refined EMT implant reconstruction showed very good agreement with the manual reconstruction. The median distance over all patients was 0.6 mm, the 95th percentile was <1 mm.

Conclusion: The refined EMT implant reconstruction proved to be accurate and fast compared to the manual reconstruction. The observed geometric deviations were in the submillimetre range and thus in the order of the human interobserver variability. The presented EMT assisted reconstruction procedure is transferable to clinical routine and has great potential to improve and streamline iBT treatment planning.

Funding Support, Disclosures, and Conflict of Interest: The electromagnetic tracking project is partially funded by an unrestricted research grant by Elekta.


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