Magnets Anchor, Maneuver Devices Inside the Body

R&D DIGEST

Although it might be hard to imagine surgery that is even less invasive than laparoscopy, a surgical system that magnetically maneuvers instruments inside the body could make this possible. The magnetic anchoring and guidance system also has the potential to leave patients with little or no scarring.

The goal of the work at the University of Texas Southwestern Medical Center (UT; Dallas) has been to develop a method and technology for laparoscopic surgery using fewer insertions. When performing a laparoscopy, the surgeon's work space is determined by the placement of each trocar. The researchers wanted to expand the limits of what a surgeon can reach inside the body, and their solution was to use magnets as a guidance and positioning system.

A stack of magnets is formed across the abdominal wall, serving as the anchor, and the instruments used in the abdomen have corresponding magnets. So instead of being fixed by the trocars, the surgeon would be able to use the magnets to move instruments wherever needed inside the abdomen via one hole. A working prototype used neodymium iron boron magnets, measuring 3.2 cm in diameter and 5.7 cm tall. The magnets used inside the abdomen measured 0.95 cm.

Possible additions to the technology include a camera system, which would eliminate the need for a laparoscope. An outside magnet would control the camera's movement, and motors could control pan, tilt, and zoom functions.

However, the latest and most promising application of magnetics is in a different field. One of the next breakthroughs could involve natural orifice transluminal endoscopic surgery (NOTES), a single-keyhole procedure. “In general surgery, it's the biggest and hottest idea,” says Jeffrey Cadeddu, MD, associate professor of urology and radiology at UT Southwestern. Instead of making an incision in the belly button, a surgeon would go through the mouth, rectum, or vagina to remove an organ, for example. One of Cadeddu's coinvestigators has successfully used the magnetics system to perform NOTES in removing gallbladders from animals.

If the concept of single-keyhole surgery takes off, the UT technology could be one of the options, Cadeddu speculates. “The conventional laparoscopic instruments and trocars for this kind of application wouldn't work,” he says. “[The technique] is going to require a whole new suite of instruments.” He suggests that the system could include three or four magnetic instruments, a special trocar to go through the orifice, and flexible cables that connect to the magnets. Robots would control the instruments.

The researchers have made improvements to the technology, but Cadeddu declined to elaborate, citing intellectual property issues.

The magnetic coupling aspect is the easy part, he says. The complicated part will be building the miniature robotic technology such as the scissors, graspers, and camera systems. The engineers at UT Arlington's

Automation and Robotics Research Institute have been working with the researchers to design instruments that could be used with the system. The team must also figure out how to create a robust package that generates strong force and torque but still fits into a small trocar.

The researchers are looking for industry partners to develop the parts of the system beyond the prototype stage. Their work is described in the March edition of the Annals of Surgery. This is the first paper on the project, which started around 2000. Cadeddu notes that a second paper about the magnetic system is scheduled to appear in the Journal of Urology this summer.

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