A GPS-like system being developed at SIUC could help surgeons navigate through the brain to find and remove everything from tumors to bullet fragments easily, cheaply, and with hardly any "cutting" at all.

"This is a project I believe could save lives," says mechanical engineering professor Ajay Mahajan of an ultrasonic-based locational system he designed with former Carbondale neurosurgeon Sumeer Lal. SIUC has filed a patent application on the invention.

Neuro-navigation is nothing new. More than a decade ago, surgeons began harnessing computers to cameras to create high-tech guides that could help them "see" what they were doing in the brain. Such precision allows them to make smaller incisions and remove only what needs to go, cutting the risk of complications and speeding healing.

But these vision-based systems are pricey and hard to maintain. The cameras take up a lot of space, and if someone moves into their sightlines or, worse, bumps them, they can lose track of where they are or shut down altogether.

"When they stop working, calibrating them again is very difficult," Mahajan says. "It only takes about five to 10 minutes, but you have the patient's head open at that point. Everything is covered in surgical drapes, so the fiducials (small markers, attached to the patient's head, that serve as preoperative calibration aids) are no longer accessible."

Mahajan's system, adapted from one he developed some years ago at Tulane University to track robots, gets rid of the cameras. It replaces them with a head restraint from which ultrasonic sensors branch off like tree limbs and adds a couple of sensors to the surgeon's probe. The two sensors on the probe act as transmitters while those on the head restraint serve as receivers, allowing the equipment to map the probe's movement through the brain in three dimensions.

"This is very much like a GPS system, except that it's indoors, and instead of satellites, we have ultrasonic receivers," Mahajan says.

Because the receivers that replace the cameras take up so much less space, sightline problems don't occur. And because they remain in place--not on the patient's head but close by--recalibration in a sterile environment is a snap.

The new system is even more accurate than the old. "In the past couple of months we've gotten it down to sub-millimeter accuracy, which is better than the old system," Mahajan says. The improved precision should make the system even more attractive to neurosurgeons.

Hospitals can pay as much as $500,000 to $750,000 for standard image-guided neurosurgery equipment. Mahajan estimates the cost of the new system would be significantly less--perhaps in the neighborhood of $50,000 to $75,000.

It will take some time before the system shows up in operating rooms. Although the finished product will work exactly the way Mahajan's experimental set-up does, it will look different.

"This project is still in its infancy--we don't even have a prototype yet," Mahajan says. "But there has been a considerable amount of interest, and as the word has gotten out, we are having companies call us about it. A big company would have the resources to develop and package it. We've shown it has a definite application; we'll let somebody else take it from there."

--by K.C. Jaehnig, Media & Communication Resources

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