Suhong Bae

A magnetic capsule endoscope (MCE) embedded with a permanent magnet (PM) can be actuated and controlled by an external magnetic field generated by a magnetic navigation system (MNS), enabling wireless examination of lesions in the gastrointestinal (GI) tract. For precise control of the MCE, accurate localization of the MCE is required, and prior researchers localized an MCE by estimating its generated magnetic field. However, it is difficult to separate the magnetic field of the MCE from that of the MNS due to modeling errors, sensor magnetization, and electronic noise. In this study, we propose a robust localization algorithm that operates even in the presence of a strong external magnetic field generated by a cylindrical PM of an MNS to actuate an MCE. We constructed a bilinear interpolation model of the external magnetic flux density measured at the central magnetic sensor when the cylindrical PM of the MNS moves along the axisymmetric plane. Then we applied coordinate transformation to predict the magnetic flux density at other sensors. Using this model, the magnetic flux density generated by the MNS can be subtracted from the measured magnetic flux density to determine that of the MCE. In addition, we incorporate a weighting factor considering the signal-to-noise ratio of the magnetic sensor into the proposed algorithm to increase the estimation accuracy of the position and orientation of the MCE. The proposed algorithm is validated through experiments with a 3×3 magnetic sensor array and a commercial MCE. We experimentally demonstrate that the proposed algorithm can estimate the position and orientation of the MCE within a clinically applicable range even in the presence of an external magnetic field to actuate an MCE.

We propose a method to control the motion of a capsule endoscope (CE) in the stomach utilizing either a single external permanent magnet (EPM) or dual EPMs to extend the examination of the upper gastrointestinal tract. When utilizing the conventional magnetic navigational system (MNS) with a single EPM to generate tilting and rotational motions of the CE, undesired translational motion of the CE may prevent accurate examination. We analyzed the motion of the CE by calculating the magnetic torque and magnetic force applied to the CE using the point-dipole approximation model. Using the proposed model, we propose a method to determine the optimal position and orientation of the EPM to generate tilting and rotational motions without undesired translational motion of the CE. Furthermore, we optimized the weight of dual EPMs to develop a lightweight MNS. We prototyped the proposed MNS and experimentally verified that the developed MNS can generate tilting and rotational motions of the CE without any translational motion.

We developed a magnetic navigation system (MNS) composed of a magnetic field control part and a robot arm part to precisely control the position and posture of a capsule endoscope (CE). The magnetic field control part generates a magnetic field by controlling the magnetization directions of dual permanent magnets (PMs) using motors, and the robot arm part supports and freely moves the magnetic field control part in three dimensions. First, we calculated the magnetic field generated by the dual PMs of the MNS by utilizing point-dipole approximation, and the magnetic force between the PMs of the MNS and the CE. We set up an optimal design problem to determine the rotational angles of the magnetization direction of the dual PMs of the MNS to align the CE to the given direction. We validated the proposed optimal design problem by utilizing finite element analysis. By using the developed MNS and a commercial CE, we measured the magnetic force acting on the CE and compared it with the simulated results of the finite element analysis. Finally, we performed a gastric endoscopy in a mimetic stomach and confirmed that the proposed MNS can effectively examine the major parts of a stomach.

This study presents a separable and recombinable magnetic robot (SRMR) to deliver and retrieve an untethered magnetic robot (UMR) to a target vascular lesion safely and effectively for robotic endovascular intervention. The SRMR comprises a delivery catheter and UMR connected to the end of the delivery catheter by a connecting section. An external magnetic field (EMF) interacts with the permanent magnet of the UMR; it can effectively generate magnetic torque and steer the delivery catheter to reach a target lesion. Furthermore, the rotating EMF allows the UMR of the SRMR to separate from the delivery catheter and perform the tunneling task. After completing the tunneling task, the UMR can be safely recombined with the delivery catheter in the vasculature via a simultaneous application of the EMF and suction force to the delivery catheter. The SRMR functions of steering, separation, movement, tunneling, drug delivery, and recombination are validated in a mimetic vascular model with a pseudo blood clot. Finally, the SRMR is successfully validated in an in vivo experiment of a mini pig's superficial femoral artery for contrast delivery, separation, movement, and recombination.