A Novel Magnetic Tracking Approach for Intra-Body Objects

Magnetic-based localization technique has been widely studied to provide accurate position and orientation information of intra-body objects, such as capsule endoscopes. However, the magnetic field decays rapidly, which is inversely proportional to the cubic of the distance. As a result, the tracking range is limited. In this paper, a magnetic servo approach is proposed for intra-body objects that move in a large volume, such as the whole digestive tract. A static tracking system formed with 8 Hall sensors is linked with a movable platform with motors. The proposed method utilizes the static tracking system to provide a precise positioning result within a small tracking range. When the distance between the object and the static tracking system exceeds a certain threshold, static tracking system will be controlled by the motors to move automatically based on a magnetic servo method to ensure accurate tracking results in a large range. Experimental results show that the proposed servo tracking method can provide a high accuracy of positioning and orientation results within a large range that as good as stationary method in small range. Within the range of 600 mm $\times500$ mm, the average position error is 2.04 mm and orientation error is 2.45°. The proposed localization method would be beneficial to the clinical examination and navigation.