Determining the Position and Orientation of In-body Medical Instruments Using Near-Field Magnetic Field Mapping

There is an increasing demand for localizing medical implants in-body, such as the wireless capsule endoscope and the Nasogastric tube. Some studies have been conducted to solve this issue using either permanent magnets, static current sources, or RF fields. The permanent magnet fails due to low power, and static current source requires a relatively high power source. The RF field source requires high frequencies to get enough precision, which undergoes high attenuation in the body. At low frequency, when the distance between the source and the receiver array is shorter than the wavelength, the far field assumption fails for localization methods. Therefore, we propose a novel method of mapping the magnetic field vector in the near field region, with which wavelength independent localization is done. We did extensive MATLAB and CST Microwave simulations followed by practical experiments. The proposed method has achieved localization accuracy of less than 1 cm in the YZ plane that is 2 cm in depth (in X -axis), and the maximum orientation error remained 10 $^\circ$ in three dimensions.