SPECIAL EDITION
Clinical Skills

By Merlina Trevino

In a few years, optical imaging could be used for everything from breast cancer diagnosis to characterization of atherosclerotic plaque. For a modality with the potential to do so much so soon, however, it's surprisingly hard to find.

Radiologists hoping to familiarize themselves with the technology would do best to seek out the specialty optics meetings and journals, according to Dr. Britton Chance, a professor emeritus of biophysics, physical chemistry, and radiologic physics at the University of Pennsylvania. Chance is developing optical imaging applications to diagnose breast cancer, hemorrhages within tissues, and brain function during cognitive activities.

Using light waves to map out tissue structures, optical imaging will eventually provide radiologists with an accurate image-capturing tool that can be used in such diverse applications as noninvasive breast cancer diagnosis and the characterization of plaque in patients at risk for atherosclerotic disease.

The flexibility of light waves is being harnessed in novel ways to aid in diagnosis: Optical coherence tomography (OCT) uses fiber-optic technology to guide light waves around corners and over long distances. Near-infrared optical imaging is used to report on the quantitative scattering and absorption of light to diagnose breast cancer.

But with all of the benefits to optical imaging, drawbacks remain. One of the largest obstacles is the photon's inability to penetrate tissue more than a few millimeters. Optical imagers must also deal with the pesky photon's tendency to scatter everywhere once it reaches its target and with the noise that is possible from ambient light.

"Research needs to provide more information on which body systems are well evaluated with optical imaging, how deep from a body surface pathology can be reliably detected, and how effectively a true imaging signal can be segregated from noise (scattered light)," said Dr. Laurie L. Fajardo, vice chair and clinical research director of breast imaging and intervention at Johns Hopkins University and incoming chair of radiology at the University of Iowa.

While many experts predict that the technology won't be ready for clinical use for another three to five years, radiologists can learn techniques that will allow them to understand and ultimately perform optical imaging. Ongoing research at institutions around the country is pushing the technique forward.

The University of Pennsylvania is one such center of research. Groups led by Dr. John Leigh, Dr. John Detre, and Dr. Arjun Yodh provide education and hands-on training on subjects from the construction of imaging to breast cancer detection and cognitive function, as well as new theoretical developments in the general field of optical imaging. These groups offer courses, seminars, and grand rounds in the application of optical tomography and spectroscopy to clinical studies.

Researchers at Johns Hopkins and Clemson University are studying the viability of near-infrared optical imaging in diagnosing breast cancer. In a study published in the February issue of Academic Radiology, lead researcher Huabei Jiang, Ph.D, and colleagues at Clemson found that using scattering and absorption parameters, they could noninvasively distinguish between breast carcinomas and benign tumors like fibroadenoma.

Because the technology is still emerging, researchers involved in optical imaging stress that residents interested in learning and understanding the most current techniques should attend scientific meetings to become familiar with the state of the art, catch up on the literature that describes current clinical studies, and get involved with a research team. Finally, radiologists can gain practical experience by participating in the optical labs or attending lab meetings at the institutions doing research in optical imaging technologies.