3D Imaging Could Improve Colorectal Cancer Screening

A new endoscopy technology called photometric stereo endoscopy (PSE), which can capture the topography of the colon surface to create a three dimensional (3D) image, could be a more robust way to screen for precancerous lesions of the colon. Researchers at the Massachusetts Institute of Technology and Harvard Medical School developed the technology to improve on the standard 2D imaging of traditional endoscopies that can sometimes miss or incorrectly classifies certain lesions.

The new technique creates both a 3D image and the standard 2D imaging, providing more information for a clinician to make a better diagnosis. The results are published in the Journal of Biomedical Optics.

According to the American Cancer Society, more than 142,000 new cases of colorectal cancer will be diagnosed in the United States this year, and more than 50,000 people will die from the disease.

Standard color video endoscope using fiber optic cameras for screening relies on color contrasts to identify precancerous and cancerous lesions but the lighting of the endoscope camera can minimize the detection of lesions with more pronounced topological changes in the colon rather than tissue coloring, according to the study authors. These missed lesions can be either protrusions or recessions in the tissue. Previous studies have shown that using computed tomography colonoscopy (CTC), which relies on topography contrasts, can increase the sensitivity of lesion detection, but this technique remains expensive and not frequently used.

Another technique, chromoendoscopy, uses surface dyes in the colon to make any topographic changes pronounced, and is more sensitive, but takes a significant amount of time per procedure.

The PSE technique can more easily detect precancerous lesions, including flatter lesions that traditional screening methods can miss, said Nicholas Durr, a research fellow at the Madrid-MIT M+Visin Consortium and the Wellman Center for Photomedicine at the Massachusetts General Hospital in Boston, Massachusetts, in a statement.

According to Durr, PSE could provide a similar contrast to the chromoendoscopy technique. “Because it's an all-optical technique, it can give the contrast at the push of a button,” he said in a statement.

The US Preventive Services Task Force (USPSTF) recommends screening for colorectal cancer at age 50 and until the age of 75. Recommended screening methods are a colonoscopy sigmoidoscopy, and high-sensitivity fecal occult blood testing.

The authors created a benchtop prototype PSE system and a modified commercial endoscope to create multiple light sources to capture images and created software to construct a 3D image of the surface of the colon. The researchers found that at least three light sources are needed for a more accurate spatial representation of the surfaces in the colon.

The utility of the system (a 14 mm–diameter colonoscope) was tested on an anatomical so-called phantom (as well as using ex vivo human tissue from surgical resections), showing that the system can detect both protruding as well as flatter lesions.

“With few changes to a commercial endoscope, PSE can be implemented to provide new information that is currently unavailable in conventional endoscopy,” stated the authors in the paper. The endoscopes need to have multiple light sources for combing the technologies.

The team is now working on additional software that could automate the process of finding lesions from the generated 3D images. The new system will be tested in a clinical trial both at the Massachusetts General Hospital and the Hospital Clnico San Carlos in Madrid.