Similar in operation to ultrasound, optical coherence tomography (OCT) is an optical technique that allows high-resolution imaging of tissue. The technique works by focusing a beam of near-infrared light (like that used in CD players) into tissue and measuring the intensity and position of the resulting reflections. To make OCT work better, UI researchers have developed injectable contrast agents that will help identify tumors early in their growth. "OCT is a relatively new technology that is just beginning to be used in the clinical setting," said Stephen Boppart, a professor of electrical and computer engineering and of bioengineering. "No doubt there will be many instances where we will need to improve the contrast."
In collaboration with UI chemistry professor Ken Suslick, Boppart and his students have developed microspheres that enhance the contrast for OCT. The tiny spheres - filled with air or some other light-scattering media - create a stronger signal than the surrounding tissue.
"We have demonstrated that our microspheres enhance the reflected signal, now we are investigating ways to modify their surface to target specific tumors," said Boppart, who also is a medical doctor and a researcher at the UI's Beckman Institute for Advanced Science and Technology. "Our goal is to design very selectable contrast agents that we can inject intravenously and that will migrate and localize to a tumor."
By enhancing contrast locally, the microspheres would permit OCT to be used both for early detection and for advanced tumor diagnostics. The higher contrast might allow researchers to noninvasively image individual cells and detect cellular changes indicative of cancer.
"As a tumor grows, its cells exhibit very specific morphological changes," Boppart said. "For example, the nuclei become much larger relative to the size of the cells, and the cells are less mature when they divide. These changes affect the scattering properties of light, which we can easily detect."
Using contrast agents, scientists might be able to study how cells migrate through tissue and metastasize, Boppart said. "Enhanced OCT imaging could even provide surgical guidance - in real time - to help find a tumor and remove all of it, without taking too much of the surrounding tissue."
In addition to developing novel contrast agents, Boppart and his students are also designing miniature probes and a more compact OCT device. Their goal is to assemble a portable unit that could be placed on a cart and wheeled into a hospital for use on patients.
Boppart presented the team's latest results at the annual meeting of the Optical Society of America, held Oct. 13-18 in Long Beach, Calif. The National Science Foundation and the Whitaker Foundation funded the research.