Intra-luminal injection of ferro-fluid for magnetic bowel retraction in minimal access surgery

Safe and effective manipulation of soft tissue during laparoscopic and other minimal access surgical (MAS) procedures can be enabled by use of electromagnetic force. We investigated magnet interaction force using finite element modeling (FEM) and tensiometer measurement, and found that our FEM results were in good agreement with measurement data. Then, we describe a novel method of ferro-magnetisation of a bowel segment for magnetic retraction. Simulated surgical procedures were carried out using an ex-vivo pig bowel model. Ferromagnetic microparticles were dispersed in a viscous carrier liquid, and injected intra-luminally to the inner (mucosal) aspect of the bowel wall. The injected magnetic microparticles were then retracted towards a magnetic probe which was located external to the bowel wall, and magnetic interaction force between the injected magnetic aggregation and the probe was found sufficient to manipulate the bowel segment. In this preliminary experiment, the probe was consisted of small Neodymium magnet discs, and magnetic attraction force can be changed by adding or reducing the number of magnet discs used. Magnetic fluids with different concentration were prepared and injected without difficulty. To solidify the magnetic aggregation, a medical grade cyanoacrylate liquid was injected sequentially and mixed in-situ with the injected microparticles aggregation underneath the magnet probe. The ferromagnetic coagulum appears to be a promising method for safe and effective magnetic bowel retraction in MAS.