Posted March 19, 2021

Viktor Gruev, Ph.D., University of Illinois at Urbana-Champaign

More than 140,000 people are diagnosed with colorectal cancer (CRC) each year in the United States, and about 50,000 will die from the disease.¹ Although imaging technologies have been introduced for screening CRC, the detection accuracy has not drastically improved, resulting in the late diagnosis of colorectal cancer and a poor prognosis. Efforts to develop high-resolution and near-infrared fluorescence sensitive endoscopes have increased in order to improve early CRC diagnosis; however, this strategy is ineffective for detecting inflammatory bowel disease -associated CRC, commonly known as colitis-associated cancer (CAC). Unlike easily detectable polyps associated with sporadic colorectal cancer, CAC lesions are highly infiltrating, multifocal, and flat. These flat lesions generally appear as normal tissue, creating an enormous challenge to detection during surveillance colonoscopy. With a Fiscal Year 2018 Peer Reviewed Cancer Research Program (PRCRP) Idea Award with Special Focus, Dr. Viktor Gruev developed a highly sensitive color-fluorescence endoscope, inspired by the mantis shrimp’s eye anatomy to detect cancerous and pre-cancerous tissue with high specificity and sensitivity in CRC and CAC patients.

Dr. Gruev saw how the mantis shrimp eyes combine very efficient photodetectors and nanoscale optical filters. Longer-wavelength light (i.e., red light) penetrates deeper into mantis shrimp eyes than shorter-wavelengths (i.e., blue light). Photosensitive cells at the top of their eyes preferentially register shorter-wavelengths, whereas photosensitive cells at the bottom of their eyes preferentially register longer-wavelength. Different parts of the eye are able to see different bands of light due to crystalline cones above the compound eye that provide fine-grained spectral filtering.^2,3 By mimicking the mantis shrimp’s multispectral capability, Dr. Gruev’s group integrated an array of vertically stacked silicon photodetectors with an array of pixelated spectral filters. Over the past year, Dr. Gruev and his team designed and developed a multi-spectral imager capable of spatially co-registered hexachromatic vision: three spectral channels in the visible spectrum (red, green, and blue) and three spectral channels in the near-infrared spectrum that can be used simultaneously to image multiple tumor-target markers. Hexachromatic vision enables differentiation across a surgical site as well as in real time, such as during image-guided surgery, allowing near-infrared images to be co-registered with visible images in both time and space, which eliminates the ambiguity between anatomical features.

Dr. Gruev’s team is currently looking to validate the ability of this imager to clearly detect the flat lesions in CAC. The use of this novel tool during routine colonoscopy has the potential to improve tumor detection sensitivity and specificity compared to current single molecular marker screening methods, enabling earlier detection and intervention for individuals with CRC or CAC.

References:

¹http://www.cancer.gov/cancertopics/types/colon-and-rectal.
²Thoen HH, How MJ, Chiou TH, et al. 2014. A different form of color vision in mantis shrimp. Science 343:411-413.
³Cronin TW and Marshall NJ. 1989. A retina with at least ten spectral types of photoreceptors in a mantis shrimp. Nature 339:137.

Link:

Public and Technical Abstracts: Bioinspired Color and Near-Infrared Endoscopy with Affibody Targeted Markers for Colorectal Cancer Surgery

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