April 30 (UPI) -- A laser light beam shined into the head to measure blood flow could be a new way to examine patients with stroke or traumatic brain injury, according to a study.
Researchers at the University of California Davis said their system is inexpensive because it uses conventional digital camera technology and fewer detectors. Their findings were published last week in the journal Optica.
The researchers have tested their device on volunteers in the laboratory, and UC Davis has already applied for a provisional patent on the technology.
"Our setup is very promising, and the cost should be lower," Dr. Wenjun Zhou, a postdoctoral researcher and associate professor at the UC Davis Department of Biomedical Engineering, said in a press release.
In the system, a laser is shined on the head as photons from the laser pass through the skull and brain in different directions. The photons become scattered by blood and tissue, and a detector somewhere else on the head picks up light fluctuations due to blood motion -- which reveals information about blood flow.
As the light signal, which is already weak, passes through skull and brain tissue, it becomes weaker. This means diffused correlation spectroscopy requires many very sensitive single photon-counting detectors. Boosting the light won't solve the problem, researchers say, because it could burn the patient's skin.
The researchers note that overlapping light waves reinforce or cancel each other out, similar to ripples on a pond.
To avoid this, the researchers split their light beam -- into a "sample" path, which goes into the patient's head, and "reference" paths, which are routed so reconnect with the sample beam before going to the detector.
Additionally, photon detectors are expensive. By boosting the signal, instead of needing about 20 photon-counting detectors that can cost a few thousand dollars each, the researchers could use a single digital camera chip.
"The strong reference light enhances the weaker signal from the sample," Zhou said.
Another advantage of the system is that the test does not need to be done in darkness and ultimately could be monitored outdoors.