Researchers at the University of Illinois at Urbana-Champaign have created a camera that mimics the complex vision system of a butterfly. The unique camera provides surgeons with a traditional color image and a near-infrared image that makes fluorescently labeled cancerous cells visible, even under bright lighting. The camera will help surgeons remove all the cancerous cells without damaging healthy tissue, making it less likely that the cancer will spread and reducing the need for multiple surgeries.
The camera offers very sensitive fluorescence detection even under standard operating room lighting and weighs less than an AA battery. Here’s the kicker, it can be manufactured for around $20. Research team leader Viktor Gruev says, “Instead of putting together commercially available optics and sensors to build a camera for image-guided surgery, we looked to nature’s visual systems for inspiration. The morpho butterfly, whose eyes contain nanostructures that sense multispectral information, can acquire both near-infrared and color information simultaneously.”
Operation
The team’s camera uses a setup similar to the butterfly eye by interlacing various nanoscale structures with an array of photodetectors, enabling collection of color and near-infrared fluorescence information on one imaging device. Integrating the detector and imaging optics into a single monolithic sensor keeps the device small, inexpensive, and insensitive to temperature changes.
The design solves sensitivity problems by allowing each pixel to take in the number of photons needed to build up an image. It doesn’t take long to create the visual-wavelength image for viewing the anatomy since the visible illumination in the lab is high. However, because fluorescence is typically dim, it takes longer to collect enough photons to build up a sufficiently bright image. By changing the exposure time to allow each pixel to detect the photons it needs, a bright fluorescence image can be created without overexposing the color image of the tissue.
Testing
The researchers tested their new instrument on a mouse paradigm that develops breast cancer spontaneously. This means that the exact location where the cancer will grow is unknown as is the number of cancer cells. Using fluorescent labels that bind to cancer cells, the researchers showed that their bioinspired imager enabled tumor detection with an accuracy and sensitivity surpassing state-of-the-art infrared cameras that are FDA approved for image-guided surgery.
The researchers also tested the ability of their infrared camera to identify lymph nodes in 11 patients with breast cancer at Washington University School of Medicine in St. Louis. Because the lymph nodes are one of the primary places where breast cancer spreads, surgeons check them to determine the cancer stage. The patients were injected with FDA-approved indocyanine green fluorescent dye that accumulates passively in the lymph nodes and then fluorescence images from the bioinspired imager were displayed either on a screen or projected onto goggles worn by the surgeons.
Gruev enlightened further, “We showed that under bright surgical lights, our instrument was 1000 times more sensitive to fluorescence than the imagers currently approved for infrared image-guided surgery. 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.”
According to the researchers, the bioinspired imager would be useful for removing various types of cancers, including melanomas, prostate cancer and head and neck cancers. Because of its small size it could also be integrated into an endoscope to look for cancer during a colonoscopy, for example.
The researchers are forming a start-up company to commercialize their bioinspired imager and are also working with the FDA to design a clinical trial in which the surgeons can compare clinical decisions made with the new imager with those that would be made with FDA-approved imagers.