Optical tomography prepares to go extraterrestrial

NASA tests lightweight brain imaging cap

Visionaries believe diffuse optical tomography (DOT) may one day compete with fMRI in the diagnosis of stroke. In the meantime, NASA is considering the technology as a means to measure health risks related to long-duration space flights.

The technology is being fashioned into a "brain cap" by engineers at the National Space Biomedical Research Institute in Houston. In preparation for use in earth orbit, the cap is being assessed by NSBRI director Dr. Jeffrey Sutton and colleagues for how well it detects brain function in real-world scenarios on earth. Ultimately, the team hopes to use the cap in space to measure neurobehavioral problems, head trauma, and changes in intracranial pressure, each of which may result from extended stays in weightlessness.

The medical systems team at the NSBRI is collaborating with Massachusetts General Hospital's Photon Migration Lab, conducting validation studies on the new technology. The underlying technology is near-infrared spectroscopy, according to Gary Strangman, Ph.D., director of the neural systems group at MGH. DOT uses a sensing probe that collects multiple overlapping near-infrared spectroscopy measurements.

Researchers expect to enroll 40 subjects in a 12- to 18-month study of the brain cap, according to Strangman. The study will look into how well the cap's performance stacks up against fMRI, now the gold standard for noninvasive measurement of brain activity.

No one expects DOT to displace fMRI, which exhibits better spatial resolution. But the brain cap has several advantages. One is portability, a definite plus when considering spaceflight. Another is cost.

"At MGH, a typical MR scan will cost on the order of $1000/hour," Strangman said. "This covers instrument upkeep, upgrades, technical personnel. DOT equipment requires virtually no upkeep and no auxiliary technical personnel."

While the researchers look forward to using the brain cap in space, most DOT research is focused on such Earth-based applications as mammography and detection of hemorrhagic or ischemic stroke. The use of the cap outside the earth's atmosphere, while promising, is probably three to five years away, according to Strangman.