Michigan
Tech Biomedical Engineering News
| Researcher Envisions Many Uses for Small Biosensors |
by John Gagnon
 Picture yourself with an aortic aneurysm, a weak spot in the vessel that bulges outward and is in danger of bursting. Your doctor has fixed it with a stent, which is like sealing off the weak spot and putting in a new, stronger channel. But what if the stent leaks? That's a problem that Keat Ghee Ong, an assistant professor in the biomedical engineering department, is addressing. He is devising a wireless sensor, the size of a small paper clip, that could be implanted by the stent. "It's a good, easy and inexpensive way to scan it to make sure there are no leaks," he says.
Wireless biosensors like these, Ong asserts, "are an accurate diagnostic tool for a lot of procedures." They measure pressure in conduits that carry blood or gastric juices or bile. There are three components: a sensor, a signal and a scanner. Ong says, "It's the same technology as an anti-theft marker in a store, but translated for medical application." His work will determine the best design, the best location, and the best purpose to embed these devices.
Ong calls these biosensors (some will be mere millimeters in size) "magnetoelastic" materials that have stress-sensing properties and give off a magnetic signal that all the scanners can pick up. Their operation is similar to the wave and scan function of new credit cards.
"There are a lot of wireless passive sensors out there," Ong notes. "Most have microprocessors and batteries and are too big. The technology is there, but it's not small enough."
A small scale is his charge. "These will be self-powered and won't require a battery or other energy source," he says. That is key because, for instance, the biggest and heaviest component of a cell phone is the battery--what Ong calls "a space hog." No battery means these sensors can indeed be fashioned in the miniature, he says.
Besides the stent pressure measurement, Ong will explore other uses for these sensors. One of these is the artificial knee. He will configure an array of thread-like sensors, in a grid pattern, to measure compression over the entire knee joint--what he calls a "pressure map" of the whole surface. Uneven pressure means uneven grinding, which could cause inflammation and, ultimately, joint failure. "I want to find out the pressure distribution so the surgeon can decide whether the knee implant is successful," he says, adding that the knee application is his biggest challenge. "We have a long way to go," he says.
The whole idea of this work, he emphasizes, is to devise a way to read pressures readily--in what he calls "real time"--by which he means recording pressure while a medical condition is manifest.
Take the sphincter of Oddi. It can shut tight and cause pain. "We know very little about how it happens, what triggers it, or what the condition of the sphincter is when that happens," he says. "The pain is now, in real time, and that's when you have to measure the pressure. By the time you get to the hospital, it might be too late."
Another wrinkle: measuring pressure when the patient is awake and functioning normally, as opposed to the current standard practice of measuring pressure with an endoscopy, which is done when the patient is sedated or asleep--"an artificially induced condition, when the body is different and doesn’t reflect the medical condition." He adds, "Tests on a sleeping or sedated person aren't particularly useful."
All in all, he concludes, "These wireless sensors will provide more accurate diagnostic procedures and will have a much better prognostic value."
He collaborates with the Mayo Clinic on the project and is supported with a $240,000 grant, good for three years, from the National Institutes of Health. He describes himself as "an engineer and problem solver." He dreamt up this project simply by talking to physicians and learning their needs and "wish lists." |
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