A localization method using 3-axis magnetoresistive sensors for tracking of capsule endoscope

In this paper, we propose a non-invasive tracking method, which has the potential to be used for localization of the capsule endoscope. The tracking system consists of a magnetic marker, a sensor array, amplifiers, data acquisition devices and a signal processing unit. The marker is modeled as a magnetic dipole to simplify the theoretical expression of the magnetic field distribution. By minimizing the squared error of the field values between the calculation and measurements using Levenberg-Marquardt optimization method, the 5 localization parameters of the dipole can be determined. Real time experiments were carried out to test the feasibility of the method. It is demonstrated that, the accuracy of the localization is related to the number of sensors. For the sensor array including 16 3-axis magnetoresistive sensors, the average position error is 3.3 mm and the average orientation error is about 3 degrees, when the magnetic marker is 100 mm above the sensor array plane.