An electromagnetic localization method for medical micro-devices based on adaptive particle swarm optimization with neighborhood search

In order to non-invasively track a medical micro-device in gastrointestinal tract, an alternating electromagnetic tracking method was presented and a prototype was developed. In the tracking method, several energizing coils were excited by time-sharing sinusoidal signal to generate varying magnetic fields by one coil and then another coil. A wireless magnetic sensor measured the magnetic field strength at the location of the micro-device. The root-mean-square value of the magnetic field strength is a high-order nonlinear system of equations with respect to the position and orientation of the micro-device. Based on the adaptive particle swarm optimization (PSO) with neighborhood search, the position and orientation of the micro-device could be obtained. The experimental results show that the tracking method is valid and the modified algorithm succeeds in dealing with the nonlinear system of equations in localization. Comparing to the standard PSO algorithm, it does not require a good initial guess to guarantee convergence. Furthermore, it has high precision and fast convergence. (C) 2011 Elsevier Ltd. All rights reserved.