Three-dimensional, miniature endoscope opens new diagnostic possibilities

Massachusetts General Hospital (MGH) researchers have developed a new type of miniature endoscope that produces three-dimensional, high-definition images, which may greatly expand the application of minimally invasive diagnostic and therapeutic procedures. In the Oct. 19, 2006, issue of Nature, the team from the Wellman Center for Photomedicine at MGH describes their prototype device and a demonstration of its use in a mouse model.

“This new ultraminiature endoscope is the first to allow three- dimensional imaging of areas inside the body, ” says Guillermo Tearney, MD, PhD, of the MGH Wellman Center, the report’s senior author. “Its ability to go places that other imaging tools cannot reach opens new possibilities for medical diagnosis and eventually treatment.”

Standard miniature endoscopic devices – which give physicians access to hard-to-reach internal organs and structures – utilize bundles of optical fibers to supply light to and transmit images from the areas of interest. Larger endoscopes that use image sensors to produce high-quality, two-dimensional images can be a centimeter or more in diameter. Existing miniature endoscopes using smaller fiber bundles may be more flexible but have difficulty producing high-quality images.

The new device developed at MGH-Wellman uses a technology called spectrally encoded endoscopy (SEE). Multicolored light from a single optical fiber – introduced through a probe about the size of a human hair – is broken into its component colors and projected onto tissue, with each color illuminating a different part of the tissue surface. The light reflected back is recorded, and the intensity of the various colors decoded by a spectrometer, which analyzes the wavelengths of light. Another device called an interferometer, which calculates structural information based on the interaction between two waves of light, provides the data required to create three-dimensional images.

To demonstrate the device’s application in a live animal, the researchers used the system to image metastatic ovarian tumors on the abdominal wall of a mouse. The SEE probe was passed into the abdominal cavity through a fine-gauge needle. The resulting three-dimensional image showed several raised areas of tumor nodules, the presence of which was confirmed by histologic analysis of the tissue.