Application of a magnetic dipole modelling approach to the problem of tracking a capsule endoscope

This paper shows that a small cylindrical permanent magnet enclosed inside a capsule can be used as a marker in endoscopy procedures. A modelling approach that treats the magnetic marker as a magnetic dipole is presented and an efficient, non-invasive, and low-cost localization method to track the capsule is proposed. A sensor array consisting of 16 magneto-resistive sensors is used to measure the magnetic field at multiple predetermined positions. The position and orientation parameters of the marker are calculated by minimizing the error between calculated and measured values of the field. The Levenberg-Marquardt optimization method is used to solve the inverse magnetic problem. Results are presented that show that the method is accurate and can be used for real-time tracking. The technique is applicable in environments that do not contain ferromagnetic materials as is the case for the human body.