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ORNL and SpectRx are developing painless test for diabetes
OAK RIDGE, Tenn.,
April 12, 1996
If you're a diabetic, you must go through an annoying ritual every three months. When you visit your doctor, a nurse pierces you with a needle and takes your blood. Then you have to wait a couple of days for the test results.
The test is the "hemoglobin A1c" procedure-a diabetic's report card. It tells your doctor how well you have controlled your diabetes over the past 90 days. If the test results are bad, the doctor may put you on a more tightly controlled diet and require you to check your glucose levels daily through a finger prick.
Tuan Vo-Dinh and his colleagues in the Health Sciences Research Division of the Department of Energy's (DOE) Oak Ridge National Laboratory (ORNL) are working with SpectRx, Inc., of Norcross, Ga., to develop a painless, noninvasive hemoglobin A1c test that is fast-it provides results in seconds, not hours. This noninvasive test being developed by SpectRx measures light emissions from an illuminated eye of the diabetic being tested using technology developed at ORNL. The ORNL technology has been licensed to SpectRx , Inc., in an agreement with Lockheed Martin Energy Research Corp., which manages ORNL for the Department of Energy.
"Our improved test should be as good as or better than the current hemoglobin A1c procedure," said Mark A. Samuels, president of SpectRx. "We believe that our system will have several advantages over the current hemoglobin A1c test. It will be noninvasive, much faster, and cheaper. It will produce no hazardous waste that is costly to dispose of, and it will eliminate exposure to blood-borne pathogens.
"There is a wealth of knowledge at ORNL that is just waiting to be developed into beneficial technology," Samuels added. "The technology for which we have a license has the potential to improve the health care for people with diabetes."
Diabetes mellitus is a disorder that affects millions of Americans. It is caused by the inability of the body to use its food efficiently because of an insufficient amount of the hormone insulin. This secretion of the pancreas gland breaks down, or metabolizes, glucose sugar from carbohydrates. Diabetics suffer from excessive thirst, hunger, loss of weight, and various problems such as heart attacks, kidney failure, and blindness. Diabetes mellitus is the leading cause of blindness.
The hemoglobin A1c test is given to diabetics routinely to determine how well the patient is maintaining long-term blood glucose levels.
"When an individual becomes diabetic, the protein molecules of the eye change because of long-term exposure to glucose," said Jonathan Eppstein, vice president of research and development for SpectRx. "The SpectRx technology enables us to detect these subtle changes in a rapid, on invasive manner."
Vo-Dinh and his colleagues, working with SpectRx, are developing the diabetes hemoglobin A1c instrument that uses synchronous fluorescence spectrometry, a technique developed by Vo-Dinh in 1978 at ORNL that was once used in England to identify sources of oil spills. The SpectRx instrument will include a new device being developed at ORNL that will provide a rapid, accurate profile of the molecular makeup of the eye, enabling a physician to measure the patient long-term glucose control levels.
"With this new device," Vo-Dinh said, "it will be possible to detect subtle changes in the eye in less than a second because our device will identify many different molecules in eye tissue at the same time."
The SpectRx device using ORNL technology would simultaneously scan the eye using light of varying wavelengths and a detector that picks up light emitted by the illuminated eye. Simply speaking, this approach is similar to illuminating a person's eye with a flashlight whose light keeps changing color and observing the color changes in the eye at the same time.
If light of a particular wavelength (color) falls on molecules in the lens of the eye, some molecules will become energized. Fluorescence occurs when these molecules return to their normal state by releasing their excess energy in the form of photons of light. Molecules will fluoresce when energized by light of different wavelengths.
A detector combined with a light source can measure the intensity of light emitted by the eye for each wavelength of light shone into it. The intensities from scanning the eye are recorded as peaks of different heights and positions in a spectrum, which resembles a range of mountains and valleys. A computer compares known spectra for normal and diabetic eyes with the spectrum from a patient's eye, allowing the determination of long-term glucose levels.
Synchronous fluorescence spectrometry, Vo-Dinh said, is superior to conventional excitation spectrometry because scanning a target simultaneously with a light source and detector, rather than separately, produces smaller, sharper peaks. Each peak in the spectrum represents molecules of a particular type.
Thanks to recent technology, Vo-Dinh and his colleagues were able to design a device that performs synchronous fluorescence spectrometry in milliseconds rather than minutes. The heart of the device is acousto-optic tunable filters, commercially made crystalline materials that can be "squeezed" by sound waves of a specific radiofrequency to select the desired wavelength of light to be passed through the crystal to the eye.
The light is transmitted into the crystal and to the eye by an optical fiber. Multidimensional detectors pick up light transmitted from the eye through an optical fiber. To automate operation of the instrument and to acquire and analyze the spectral data, special computer software is being developed by ORNL postdoctoral scientists Dennis Hueber and Chris Stevenson.
SpectRx plans to develop a compact counter-top or hand-held device that combines a low-cost light source that is safe for the eye with a detector that receives light emitted by the eye.
The program is funded by DOE's Office of Health and Environmental Research.
ORNL, one of the Department of Energy's multiprogram research laboratories, is managed by Lockheed Martin Energy Research Corp.