Improved electromagnetic tracking for catheter path reconstruction with application in high-dose-rate brachytherapy.

Area of Science:

• Medical Imaging
• Robotics
• Signal Processing

Background:

• Electromagnetic (EM) catheter tracking is crucial for reconstructing catheter paths in clinical interventions.
• EM tracking is susceptible to measurement errors, impacting procedural outcomes.
• Improving catheter path reconstruction accuracy is essential for patient safety and treatment efficacy.

Purpose of the Study:

• To develop and evaluate a nonholonomic extended Kalman filter (EKF) for minimizing catheter tracking errors.
• To enhance the accuracy and precision of electromagnetic catheter path reconstruction.
• To assess the robustness of the EKF method against varying sensor velocities and path curvatures.

Main Methods:

• An extended Kalman filter (EKF) was formulated using nonlinear kinematic models and nonholonomic motion constraints of an EM sensor.
• Experimental validation was performed in a clinical HDR suite using a phantom with varying catheter curvatures.
• The nonholonomic EKF was applied to tracking data from an Ascension trakSTAR EM sensor at different speeds.

Main Results:

• The nonholonomic EKF achieved a path reconstruction accuracy of 1.9 mm, outperforming manufacturer's filters (2.4 mm) by 21% and raw EM measurements (3.5 mm) by 46%.
• Path reconstruction precision was improved to 0.8 mm with the EKF, surpassing manufacturer's filters (1.0 mm) by 20% and raw EM measurements (1.7 mm) by 53%.
• Reconstruction accuracy was primarily influenced by EM field transmitter position, not sensor velocity or path curvature.

Conclusions:

• The nonholonomic EKF effectively reduces EM measurement errors in catheter path reconstruction.
• The method demonstrates robustness to path curvature and sensor speed, operating in real-time.
• This approach shows promise for various clinical procedures, including cardiovascular interventions, pulmonary applications, and brachytherapy.