Scuba divers, airplane pilots and people in submarines all can experience decompression sickness when their bodies are subjected to sudden, drastic changes in the surrounding air or water pressure. The condition can be fatal, but researchers led by Kirill Larin at the University of Houston are working to develop a system to diagnose it in a matter of seconds so that actions can be taken before the symptoms arise.

They are using a grant from the US Navy to develop a noninvasive tool based on OCT for eventual testing on humans. In preliminary testing, they demonstrated that OCT can locate the presence of nitrogen gas in blood and tissues, which during decompression sickness can restrict the flow of blood throughout the body and can cause damage.

The system they are developing performs one scan of a broadband swept-source 10-mW Santec laser over wavelengths from 1245 to 1355 nm at a rate of 15 kHz. An interferometer splits the laser light into a reference arm and a sample arm. Light returned from both arms forms an interferogram, which is detected by a Thorlabs balanced-receiver configuration that reduces the source intensity noise as well as the autocorrelation noise from the sample. Analyzing the interferogram and scanning the beam across the sample’s surface allow the reconstruction of images with high depth and lateral resolution. The system enables the researchers to extract phase information as well.

An early version of the tool has located nitrogen bubbles as small as 6 μm (most bubbles are between 5 and 15 μm). Although the system currently is constructed on an optical table, Larin said that, after in vitro and in vivo animal feasibility studies have been conducted, the experimental prototype could be turned into a smaller bedside device for clinical studies.