Author: Justus Adamson, Wesley Andrew Cunningham, Chang-Sei Kim, Yeongoh Ko 👨🔬
Affiliation: Duke University, Chonnam National University, Duke University Medical Center 🌍
Purpose: Toxicity to bowel remains a challenge for radiotherapy, particularly for abdominal SBRT . We propose a noninvasive method to reposition bowel using a remote magnetic navigation system (RMNS) with a magnetic capsule robot (MCR); this work presents conceptual design, proof of principle experiments, and feasibility analysis.
Methods: We designed an RMNS for wireless actuation composed of a robotic arm and four electromagnetic coils, each made of an iron core wound with 571 turns of wire, capable of permitting a maximum operating current of 10A. An MCR intended for insertion in the bowel was devised containing a neodymium magnet (9mm diameter, 18mm length) comparable to commercialized capsule endoscopy. We calculated the magnetic force that can be generated by the RMNS in COMSOL Multiphysics. The distance between the external robotic RMNS and the MCR was set to range from 0-150mm. We compared the computed magnetic force and the required force, where the required force is measured by a force sensor through ex-vivo experiments. Finally, preliminary lifting and pulling experiments were conducted for possible implementation.
Results: The measured force required to lift an ex-vivo porcine small intestine was 0.22N while the pulling force required to move 1–5 strands of intestine ranged from 0.13N-0.58N. In comparison, the computed magnetic force that can be generated by the RMNS ranged from 8N at a distance of 0mm to 0.25N at 65mm, respectively. Through the ex-vivo experiment with the proposed system, we demonstrated that the intestine was successfully lifted and moved in the desired direction under the magnetic force control applied to the MCR.
Conclusion: Our analysis indicates that the proposed system can generate sufficient force to move intestine within a limited distance applicable to SBRT. This study highlights the potential applicability of the RMNS for sparing nearby bowel during targeted radiotherapy.