Active 6-DoF Electromagnetic Pose Tracking Using Orientation Control of the Magnetic Source

Electromagnetic pose tracking has been widely used to localize various intra-body medical instruments for accurate guidance during operation. Conventionally, stationary electromagnetic coils are used as magnetic sources and the magnetic sensor is attached to the target to measure the magnetic field for pose estimation. Although it is well known that the magnetic sensitivity and the tracking accuracy deteriorates with the increase of the distance between the sensor and the electromagnet, the dependence of magnetic sensitivity and tracking accuracy on the direction of sensor relative to the electromagnet is long overlooked. In this paper, the direction-related magnetic sensitivity variation in the single-magnet pose tracking system is analytically investigated. It is found that the magnetic sensitivity to the pose of the sensor is the highest when the sensor lies exactly on the axis of the magnetic moment of the electromagnet, and it decreases as the sensor moves to the side of the electromagnet. Therefore, to maintain the highest sensitivity and accuracy in any direction of the sensor, an active electromagnetic tracking system is developed by controlling the orientation of the electromagnet to always point towards the sensor. Simulation results show that the proposed active tracking strategy can achieve uniformly high tracking accuracy around the magnetic source.