MIT researchers have developed a new endoscopy technology that can capture topographical images of the colon surface as well as traditional two-dimensional images. These images make it easier to see precancerous growths, including some of the flatter lesions that traditional endoscopy misses.
Colorectal cancer kills around 50,000 people each year in the United States (16,000 in the UK). Early detection of precancerous lesions has been shown to reduce the death rates from colorectal cancer. While it's quite easy to spot large polyps (protruding growths) that grow in the colon, many studies have shown that much more subtle, flat or sunken lesions can also cause cancer.
Traditional colonoscopies use endoscopes with fibre-optic cameras to capture 2D images. There is another technique called chromoendoscopy, where dye is sprayed in the colon, that can highlight topographical abnormalities, but it is not used terribly often as it can take a long time.
The new technique is called photometric stereo endoscopy. It works by measuring the distances between multiple light sources (three) and the surface. These distances can be used to calculate the slope of the surface relative to the light source, which means lumps, bumps and lesions can be documented. The technology was originally a computer vision technique, but researchers adapted it for endoscopy purposes in order to eliminate distortions which occur because there's no way to know the precise distance between the tip of the endoscope and the colon surface.
They did this by finding a way to filter out spatial information from the smoothest surfaces. The resulting tool doesn't calculate the exact height or depth of surface features, but it does create a visual representation of the colon that allows a doctor to determine if there are any precancerous lesions.
"Photometric stereo endoscopy can potentially provide similar contrast to chromoendoscopy. And because it's an all-optical technique, it can give the contrast at the push of a button," explains Nicholas Durr, a research fellow in the Madrid-MIT M+Vision Consortium, a community of researchers investigating biomedical imaging.
The prototypes were found to be effective at mapping the shape of the colon when tested on an artificial silicon colon. Durr said that the technology could be incorporated into newer endoscopes that have multiple light sources. "From a hardware perspective all they need to do is alternate the lights and then update their software to process this photometric data."
The research team is going to test the technology on human patients in clinical trials in Massachusetts General Hospital and Hospital Clinico San Carlos in Madrid. They are also working on developing algorithms that could help to automate the lesion identification process.
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