Bio-Inspired Imager Improves Cancer Surgery

A new camera that mimics the intricate visual system of a butterfly can improve sensitivity in near-infrared (NIR) fluorescence image-guided surgery, claims a new study.

Developed at the University of Illinois (UI; Urbana-Champaign, USA) and Washington University in St. Louis (WUSTL; MO, USA), the new camera is comprised of an artificial multispectral sensor--inspired by the Morpho butterfly’s compound eye--that interlaces nano-scale spectral tapetal filters with a photodetector array, thus enabling collection of color and NIR fluorescence information on one imaging device. The single-chip multispectral imager is 1,000 times more sensitive and offers seven times better spatial co-registration accuracy than current clinical imaging systems.

The unique design allows each pixel to take in the number of photons needed to build up an image; by changing exposure time so as to allow each pixel to detect the photons necessary, bright fluorescence images can be created without overexposing the color image of the tissue. Testing showed the camera seamlessly integrates into the surgical workflow, providing real-time information on cancerous tissue and sentinel lymph nodes. Integrating the detector array and optics into a single sensor makes it small, inexpensive, and insensitive to temperature changes. The study was published in the April 2018 issue of Optica.

“We realized that the problems of today's infrared imagers could be mitigated by using nanostructures similar to those in the Morpho butterfly. Their compound eyes contain photoreceptors located next to each other such that each photoreceptor senses different wavelengths of light in a way that is intrinsically co-registered,” said lead author Missael Garcia, PhD, of UI. “The bioinspired imager would be useful for removing various types of cancers, including melanomas, prostate cancer, and head and neck cancers.”

"During surgery, it is imperative that all the cancerous tissue is removed, and we've created an imaging platform that could help surgeons do this in any hospital around the world because it is small, compact and inexpensive,” said senior author Professor Viktor Gruev, PhD. “Under bright surgical lights, our instrument was 1,000 times more sensitive to fluorescence than the imagers currently approved. Because the bioinspired imager can reveal fluorescence that is deep in the tissue, it sped up the process of lymph node identification and helped surgeons find lymph nodes that couldn't be seen by eyesight alone.”

Image-guided surgery can enhance cancer treatment by decreasing, and ideally eliminating, positive tumor margins and iatrogenic damage to healthy tissue. Current state-of-the-art NIR fluorescence-imaging systems are bulky and costly, lack sensitivity under surgical illumination, and lack co-registration accuracy between multimodal images. As a result, an overwhelming majority of physicians still rely on unaided vision and palpation as primary sensing modalities for distinguishing cancerous from healthy tissue.

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University of Illinois
Washington University in St. Louis