Real time endoscope capsule localization using the electromagnetic field method

Capsule endoscope systems require localization within the gastrointestinal tract in order to efficiently identify lesions. Commercialized capsule systems presently use the radio signal strength indicator to track the capsule, which has limited accuracy. Methods based on X-Rays, Gamma-Rays, MRI, ultrasound, and visible wave methods are expensive and may pose a health risk with long-term exposure. The permanent magnet method provides satisfactory accuracy but is limited in range and is susceptible to interference. In this thesis, an electromagnetic tracking system is proposed to overcome the limitations of permanent magnet methods. The six-degree-of-freedom localization system consists of three concentric orthogonal transmitting and sensing coils. The measurement range of this arrangement is only dependent on the transmitter and sensing coil geometries. An algorithm is described for optimizing the transmitter parameters such the geometry, applied power, frequency, and the available volume. A triaxial arrangement of sensor coils is then described which provides 59% more measurement range than traditional cylindrical coils. Resonance-coupling is also investigated to passively increase the induced voltage and enhance the measurement range. A consequence of resonance enhancement is an increased settling time which reduces the measurement rate. A resistive tuning method is proposed to control the trade-off between gain and settling time. Experimental results are presented throughout to clarify and validate the concepts presented.