Photometric stereo endoscopy is a technique that captures information about the high-spatial-frequency topography of
the field of view simultaneously with a conventional color image. Here we describe a system that will enable
photometric stereo endoscopy to be clinically evaluated in the large intestine of human patients. The clinical photometric
stereo endoscopy system consists of a commercial gastroscope, a commercial video processor, an image capturing and
processing unit, custom synchronization electronics, white light LEDs, a set of four fibers with diffusing tips, and an
alignment cap. The custom pieces that come into contact with the patient are composed of biocompatible materials that
can be sterilized before use. The components can then be assembled in the endoscopy suite before use. The resulting
endoscope has the same outer diameter as a conventional colonoscope (14 mm), plugs into a commercial video
processor, captures topography and color images at 15 Hz, and displays the conventional color image to the
gastroenterologist in real-time. We show that this system can capture a color and topographical video in a tubular colon
phantom, demonstrating robustness to complex geometries and motion. The reported system is suitable for in vivo
evaluation of photometric stereo endoscopy in the human large intestine.
While color video endoscopy has enabled wide-field examination of the gastrointestinal tract, it often misses or incorrectly classifies lesions. Many of these missed lesions exhibit characteristic three-dimensional surface topographies. An endoscopic system that adds topographical measurements to conventional color imagery could therefore increase lesion detection and improve classification accuracy. We introduce photometric stereo endoscopy (PSE), a technique which allows high spatial frequency components of surface topography to be acquired simultaneously with conventional two-dimensional color imagery. We implement this technique in an endoscopic form factor and demonstrate that it can acquire the topography of small features with complex geometries and heterogeneous optical properties. PSE imaging of ex vivo human gastrointestinal tissue shows that surface topography measurements enable differentiation of abnormal shapes from surrounding normal tissue. Together, these results confirm that the topographical measurements can be obtained with relatively simple hardware in an endoscopic form factor, and suggest the potential of PSE to improve lesion detection and classification in gastrointestinal imaging.