WE-AB-BRA-10: Assessment of Fiber Bragg Grating (FBG)-Based Sensing for Real-Time Needle Tracking During MR-Guided Brachytherapy

Purpose: This study assesses the potential of Fiber Bragg Grating (FBG)-based sensing for real-time needle (including catheter or tube) tracking during MR-guided HDR brachytherapy. Methods: The proposed FBG-based sensing tracking approach involves a MR-compatible stylet composed of three optic fibers with nine sets of embedded FBG sensors each. When the stylet is inserted inside the lumen of the needle, the FBG sensing system can measure the needle's deflection. For localization of the needle in physical space, the position and orientation of the stylet base are mandatory. For this purpose, we propose to fix the stylet base and determine its position and orientation using a MR-based calibration as follows. First, the deflection of a needle inserted in a phantom in two different configurations is measured during simultaneous MR-imaging. Then, after segmentation of the needle shapes on the MR-images, the position and orientation of the stylet base is determined using a rigid registration of the needle shapes on both MR and FBG-based measurements. The calibration method was assessed by measuring the deflection of a needle in a prostate phantom in five different configurations using FBG-based sensing during simultaneous MR-imaging. Any two needle shapes were employed for the calibration step and the proposed FGB-tracking approach was subsequently evaluated on the other three needles configurations. The tracking accuracy was evaluated by computing the Euclidian distance between the 3D FBG vs. MR-based measurements. Results: Over all needle shapes tested, the average(standard deviation) Euclidian distance between the FBG and MR-based measurements was 0.79mm(0.37mm). The update rate and latency of the FBG-based measurements were 100ms and 300ms respectively. Conclusion: The proposed FBG-based protocol can measure the needle position with an accuracy, precision, update rate and latency eligible for accurate needle steering during MR-guided HDR brachytherapy. M. Borot de Battisti is funded by Philips Medical Systems Nederland B.V.; M. Moerland is principal investigator on a contract funded by Philips Medical Systems Nederland B.V.; G. Hautvast and D. Binnekamp are fulltime employees of Philips Medical Systems Nederland B.V.