Hybrid Localization of Microrobotic Endoscopic Capsule Inside Small Intestine by Data Fusion of Vision and RF Sensors

Wireless capsule endoscope (WCE) offers a noninvasive investigation of the entire small intestine, which other conventional wired endoscopic instruments can barely reach. As a critical component of the capsule endoscopic examination, physicians need to keep track of the 3D trajectory that the capsule has traveled inside the lower abdomen to identify the positions of the intestinal abnormalities after they are found by the video source. However, existing commercially available radio frequency (RF)-based localization systems can only provide inaccurate and discontinuous position estimation of the WCE due to nonhomogeneity of body tissues and highly complicated distribution of the intestinal tube. In this paper, we present a hybrid localization technique, which takes advantage of data fusion of multiple sensors inside the WCE, to enhance the positioning accuracy and construct the 3-D trajectory of the WCE. The proposed hybrid technique extracts motion information of the WCE from the image sequences captured by the capsule's embedded visual sensor and combines it with the RF signal emitted by the wireless capsule, to simultaneously localize the WCE and mapping the path traveled by the WCE. Experimental results show that the proposed hybrid algorithm is able to reduce the average localization error from 6.8 cm to <2.3 cm of the existing RF localization systems and a 3-D map can be precisely constructed to represent the position of the WCE inside small intestine.