Concept and simulation study of a novel localization method for robotic endoscopic capsules using multiple positron emission markers Trung Duc Than a) and Gursel Alici b) School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, New South Wales 2522, Australia Steven Harvey c) Department of Nuclear Medicine, Wollongong Hospital, New South Wales 2500, Australia Hao Zhou d) and Weihua Li e) School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, New South Wales 2522, Australia (Received 7 November 2013; revised 13 May 2014; accepted for publication 15 May 2014; published 6 June 2014) Purpose: Over the last decade, wireless capsule endoscope has been the tool of choice for noninvasive inspection of the gastrointestinal tract, especially in the small intestine. However, the latest clinical products have not been equipped with a sufficiently accurate localization system which makes it difficult to determine the location of intestinal abnormalities, and to apply follow-up interventions such as biopsy or drug delivery. In this paper, the authors present a novel localization method based on tracking three positron emission markers embedded inside an endoscopic capsule. Methods: Three spherical 22 Na markers with diameters of less than 1 mm are embedded in the cover of the capsule. Gamma ray detectors are arranged around a patient body to detect coincidence gamma rays emitted from the three markers. The position of each marker can then be estimated using the collected data by the authors’ tracking algorithm which consists of four consecutive steps: a method to remove corrupted data, an initialization method, a clustering method based on the Fuzzy C-means clustering algorithm, and a failure prediction method. Results: The tracking algorithm has been implemented in MATLAB utilizing simulation data gen- erated from the Geant4 Application for Emission Tomography toolkit. The results show that this localization method can achieve real-time tracking with an average position error of less than 0.4 mm and an average orientation error of less than 2 ◦ . Conclusions: The authors conclude that this study has proven the feasibility and potential of the pro- posed technique in effectively determining the position and orientation of a robotic endoscopic cap- sule. © 2014 American Association of Physicists in Medicine.[http://dx.doi.org/10.1118/1.4881316] Key words: wireless capsule endoscope, tracking, localization, positron emission markers, robotic capsule 1. INTRODUCTION A wireless capsule endoscope (WCE), being a noninvasive and well-tolerated diagnostic tool, has been a preferred choice to investigate abnormalities in the gastrointestinal (GI) tract since its introduction in 2000. 1 Over a million of examina- tions using WCE have been performed all over the world. 2 Although many patients have benefited from these examina- tions, deaths caused by GI diseases and disorders are still at a high rate. It was reported by the World Health Organization that there were more than 1.4 × 10 6 deaths caused by stom- ach and colorectal cancer in 2009. 3 The American Cancer So- ciety also reports that approximately 50 000 people die each year in the United States due to colorectal cancer. 4 Addition- ally, other site-specific GI diseases also impose a substantial health burden on the society. Therefore, the next generation of WCE is desired to have not only the diagnostic functionality, but also the therapeutic capabilities such as biopsy, targeted drug delivery, and micro surgery. 5–7 A major issue that constrains the progress to develop a fully robotic WCE is that it has not been equipped with an accurate localization system to provide both position and ori- entation information of the capsule. With the latest version of WCE, the endoscopists are able to detect pathologies by reviewing the clear images of abnormalities in the GI tract. However, they are presently unable to locate the abnormali- ties accurately which, to some extent, limit the effectiveness of the diagnosis. One of the important information that the endoscopist needs during the diagnosis is the distance that the capsule has traveled along the GI tract. It would be possible to estimate this information and reconstruct the movement tra- jectory if the capsule is tracked continuously in real time. Fur- thermore, in some cases, the endoscopists may want to return to the sites of interest for further diagnosis or follow-up inter- ventions. Without accurate localization data, it is very difficult to accomplish this capability. Another limitation of the current commercial endoscopic capsules is their passive movement driven by natural peristal- sis of the GI tract. Endowing the capsule with an active ac- tuation system would speed up the endoscopic examination and minimize the possibility of missing symptoms. It would also greatly reduce the risks of retention. 8 However, an active 072501-1 Med. Phys. 41 (7), July 2014 © 2014 Am. Assoc. Phys. Med. 072501-1 0094-2405/2014/41(7)/072501/14/$30.00