Miniature implantable sensor likely lifesaver for patients

Using a tiny wireless sensor developed at Oak Ridge National Laboratory, doctors will know in minutes instead of hours if an organ is getting adequate blood flow after transplant or reconstructive surgery.

Conventional methods for assessing circulation involve invasive procedures or extensive laboratory testing. In some cases, by the time doctors realize there isn’t adequate blood flow to an organ or tissue, irreversible damage already has occurred.

“Our goal is to offer a technique that provides the physician with a very early indication of whether the surgery is successful,” said Nance Ericson, who leads the effort from ORNL’s Engineering Science and Technology Division. Ericson is working with Mark Wilson, a surgeon at the University of Pittsburgh, and Gerard Coté of Texas A&M University.

The tiny implantable sensor – about the diameter of a quarter — and micro-instrumentation being developed by Ericson would provide real-time information by transmitting data to a nearby receiver. Specifically, the unit employs optical sensors to assess tissue circulation. Preliminary tests using laboratory rats have provided encouraging results.

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

While Wilson provides the practicing medical component required in this research, Coté, who heads the optical biosensing laboratory within the Department of Biomedical Engineering at Texas A&M, provides expertise in modeling, post-processing and sensor optimization. Ericson and ORNL colleagues bring to the team vast knowledge in engineering, signal processing, system design, radio frequency telemetry design, and fabrication and micro-fabrication techniques.

Over the next year, Ericson will be working to miniaturize the sensors and associated electronics, which will enable surgeons to implant the sensor in the precise area of interest, either as a subdermal or deep-tissue implant. Ericson envisions the sensor remaining in the body, which would avoid additional surgery; however, that is an area that may require additional evaluation. Other efforts include biosensor optimization, design of low-power highly miniaturized signal processing and telemetry electronics, and development of encapsulation techniques.

Once they have made sufficient progress in these areas, the research team plans to conduct additional testing of the sensing techniques to demonstrate clinical significance. Finally, the procedure would be subject to clinical trials and Food and Drug Administration approval.

Assuming the technology passes all the tests, Ericson envisions this work leading to significant benefits.

“This research is based on several key developments in optics and micro-fabrication that have far-reaching implications for future directions in a multitude of clinically significant biomedical sensing systems,” Ericson said. “Through these innovations, biomedical microsensors are poised to make major technology advances to help meet the critical needs of patients in hospitals, emergency care facilities and extended-care facilities.”

The ability to prevent — or at least detect — circulation problems quickly could lead not only to fewer complications during surgery, but also could reduce the number of deaths attributable to those complications.

Although not a part of this project, Ericson sees this leading to several other photonics-based microsensors for making measurements in a number of areas. For example, this approach could be useful for measuring arterial blood gases, which are primary indicators of respiratory function, or serum lactate, which is a marker for the severity of tissue injury. Current methods require obtaining blood samples and then sending those samples to a lab for analysis.

Funding for this research is provided by DOE’s Office of Science. Initial funding began in 1997 through ORNL’s Laboratory Directed Research and Development program, also funded by DOE.

ORNL is a DOE multiprogram research facility managed by UT-Battelle.