Quasi-Static Magnetic Localization of Capsule Endoscopes with an Active Integrated Coil

The reliable localization for capsule endoscopes is an open research topic. In this study, a low-frequency magnetic localization method for capsule endoscopes with an integrated active coil is proposed. The spatial constraint, the limited battery capacity and the ferromagnetic battery shell of commercial capsules were considered. The generated magnetic flux density was evaluated depending on the distance to the coil and the maximal detectable range was determined. Twelve sensors were arranged in rings and by comparing the measured magnetic flux density with the analytic dipole model, the position and orientation of the coil were reconstructed. The results revealed that the ferromagnetic shell increases the magnetic moment of the coil by approximately a factor of 2.4. Moreover, the mean position and orientation errors were 0.5 mm and 0.3°. Furthermore, by using only the three closest sensors to the coil, a similar localization performance was achieved. Therefore, it was concluded that it is a feasible approach to choose the sensors, which measure the strongest signal to address the problem of the maximal detectable range of magnetic sensors. Moreover, by considering the limited battery capacity, the localization with the proposed coil must be conducted in short time intervals instead of continuously.