Development of a magnetic intra-uterine manipulator

[摘要] ENGLISH ABSTRACT:Uterine manipulation is integral to obtaining adequate access to the uterusduring a laparoscopic procedure. A variety of mechanical manipulators havebeen developed to aid the surgeon with the dissection of the uterus duringlaparoscopic hysterectomies. Limitations of existing manipulators are thatthey require an additional assistant during surgery, are expensive and maycause tissue trauma to the vaginal or cervical canal. This study introduces thenovel concept of a magnetic uterine manipulator, intended to overcome existingdevices' shortcomings and enabling non-invasive uterine manipulation.The first goal of the study was to investigate the strengths and weaknesses ofexisting mechanical manipulators and compare them to those of a magneticdevice. Analysis showed that a magnetic manipulator would not be able tocompete in terms of the range of motion of existing devices. A limited anteriorsagittalrotation range of 60was seen in the magnetic manipulator comparedto a range of 140in mechanical devices. However, the magnetic manipulatorcould eliminate the need for an extra assistant, is reusable and thus also moreeconomical. The second goal was to investigate which type of setup would bemost successful at effective uterine manipulation. Through concept analysis acart-on-arch system was deemed most effective. To lift an effective load of 1N over an air-gap of 150 mm rare-earth N38 Neodymium (NdFeBr) magnetsshowed the most promise as magnetic actuators. FEA (Finite Element Analysis)simulations of the magnetic setup were validated experimentally whichproduced an acceptable MAE (mean absolute error) of 0.15 N. Furthermore,a comparative simulation study of shielded and unshielded magnets was donewhich concluded that shielded magnets produce a slightly higher attractionforce and would be safer to use due to less magnetic flux fringing. Thirdly andlastly, potential safety hazards and risks of using magnetic actuators in surgical environments were identified. The literature research revealed that connectionsbetween magnetic fields and health risks to patients have not been conclusivelyproven in clinical studies to date, but nonetheless, great care should be takenin situations where the patient has a pace-maker or orthopaedic implants, asthese might interact with the magnetic field. Recommendations for futurework include further research into the geometry and scaling effects of magneticshielding as well as electromagnetic actuator design. Electromagneticactuators could replace rare-earth magnets, if coil and cooling systems are optimized,resulting in magnets that can be reversed or switched off and whichare therefore easier to control and safer to handle.

[发布机构] Stellenbosch University