Real-time and accurate endoscope electromagnetic tracking via marker-free registration based on endoscope tip center

Abstract

This paper proposes an improved marker-free registration framework that uses the center of an endoscope tip to establish a spatial alignment between an electromagnetic tracker and pre-operative images (e.g., computed tomography). To obtain such an alignment, currently available marker-free registration methods assume that endoscopes are operated along the centerline of hollow organs (e.g., airway trees). However, such an assumption fails easily during clinical interventions. To tackle such an assumption, we estimate the position of the endoscope tip center in terms of each measurement of an electromagnetic sensor that is attached at the endoscope tip since the center position is usually closer to the organ centerline than the sensor measured position. our experimental results from phantom validation demonstrate that our simple idea of using the position of the endoscope tip center to perform the marker-free registration was very effective, reducing the tracking error significantly from at least 6.3 to 4.0 mm compared to currently available methods.