Implant could monitor transplant status

Nov. 6, 2002 at 6:04 PM
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OAK RIDGE, Tenn., Nov. 6 (UPI) -- A development team of government and academic researchers is testing early versions of a miniaturized, wireless blood-flow sensor to help doctors monitor transplanted tissue, researchers said Wednesday.

The device's optical components could measure oxygen levels and blood flow inside a donor organ, with a transmitter sending the data to a bedside receiver, said Nance Eriscon, a senior development staff member at Oak Ridge National Laboratory and principal investigator on the project.

The team already has tested wired versions of the device in laboratory rats, Ericson told United Press International.

"We're trying to create something that tells a physician, 'There's a potential problem here, use the more precise tools you have,' so we can figure out what's going on and change the outcome for the patient," Ericson said. "I'm confident we can make (the implant) small enough. The issue is ... will it provide information early enough to help the patient?"

The original prototype was roughly the size "of a Big Mac box," Ericson said, but the first round of miniaturization took the device down to 1 inch by 2 inches by 3/4 of an inch. The working goal for the team is something about the size of four stacked 25-cent pieces, he said, to ensure the design is robust enough for a medical environment.

Nance's team includes Mark Wilson, a surgeon at the University of Pittsburgh, and Gerald Cote, a sensor optimization and signal-processing researcher at Texas A&M University in College Station. The ORNL staff is contributing its skills in system engineering, radio-frequency telemetry and other fields.

"Although we have more work to do, we are extremely optimistic that this technology will dramatically improve physicians' ability to care for critically ill patients," Wilson said.

One of the main challenges is ensuring the radio transmitter and the sensor's light-emitting diodes, which generate heat during operation, remain compatible with living tissue, Ericson told UPI.

The current plan is to use several frequencies to ensure usable data reaches the receiver, Ericson said, but the need to keep power usage -- and therefore heat -- at reasonable levels complicates that choice. A possible solution would cycle the sensors and transmitter off and on to limit heat buildup, he said. An ORNL team member is well versed in the standards for protecting tissue, so the final product will be safe, he said.

Although physicians already have tools for detecting whether or not an organ is getting enough blood, the wireless sensor could be seen as a blood-flow version of electrical heart- and brain-function monitors, said Dr. Peter Whitington, director of Northwestern University's Transplant Center. About 500 of the 900 liver transplants Whitington has performed have involved a non-invasive scanner to monitor the organ immediately after surgery, he told UPI.

When doctors learn to interpret the wireless device's data, it could add valuable detail to the health level of a donor organ, but it "wouldn't necessarily send someone back to the O.R. to try and find a damaged blood vessel," Whitington said.

An apparent limitation to the device lies in the often uneven delivery of blood to a transplant, Whitington said. If the sensor is implanted in an area of the organ that happens to receive poor circulation, it could report trouble when the organ is actually functioning well, he said.

(Reported by Scott R. Burnell, UPI Science Writer, Washington)

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