Electromagnetic Tracking of Series Inductive Sensors for Catheter Shape Sensing

Flexible medical devices require accurate real-time shape feedback during minimally invasive procedures. Conventional fluoroscopic imaging, while used, is limited to 2D views and exposes users to ionising radiation. Fibre-Bragg grating sensing provides a radiation-free alternative but demands complex and costly systems. A purely electromagnetic approach is introduced that uses three uniaxial inductive sensors connected in series, which reduces wiring complexity by requiring only two conductors, regardless of sensor count. This series-connected sensor configuration substantially reduces wiring complexity and acquisition hardware demands, however, it necessitates greater field generation requirements and incurs longer solver runtimes. A lumped parameter model for series-connected sensors is introduced and validated experimentally through impedance measurements, demonstrating minimal amplitude and phase distortion below 10 kHz. The open-source Anser electromagnetic tracking (EMT) platform is extended by using three planar field generators (totaling 24 coils) and implementing a novel objective function that simultaneously estimates the position and orientation of three series sensors. Static accuracy evaluations conducted over a volume of 200 mm × 200 mm × 100 mm yielded mean errors below 2.2 mm, while mean errors in dynamic assessments were below 1.2 mm. These results constitute an initial step toward compact and accurate shape sensing for flexible catheters in endovascular interventions.