Colonoscopies are credited for saving thousands of lives every year by making early diagnoses of cancerous polyps. Yet, lesions that don’t visually “pop-out” from two dimensional imaging can also develop into full blown cancer.
A team from Madrid-MIT M+Vision Consortium, a Boston/Madrid collaboration of researchers, has developed a new endoscope that provides both 2D and volumetric imaging of the interior colon wall thanks to a technique called photometric stereo endoscopy.
Originally developed as a computer vision technique, photometric stereo imaging can reproduce the topography of a surface by measuring the distances between multiple light sources and the surface. Those distances are used to calculate the slope of the surface relative to the light source, generating a representation of any bumps or other surface features.
However, the researchers had to modify the original technology for endoscopy because there is no way to know the precise distance between the tip of the endoscope and the surface of the colon. Because of this, the images generated during their first attempts contained distortions, particularly in locations where the surface height changes gradually.
To eliminate those distortions, the researchers developed a way to filter out spatial information from the smoothest surfaces. The resulting technology, which requires at least three light sources, does not calculate the exact height or depth of surface features but creates a visual representation that allows the colonoscopist to determine if there is a lesion or polyp.
The researchers built two prototypes — one 35 millimeters in diameter, which would be too large to use for colonoscopy, and one 14 millimeters in diameter, the size of a typical colonoscope. In tests with an artificial silicon colon, the researchers found that both prototypes could create 3-D representations of polyps and flatter lesions.
Journal of Biomedical Optics: Photometric stereo endoscopy