The camera was tested in mice and in human patients with breast cancer. The study was published in the journal Optica.
"By looking at the way nature has designed the visual systems of insects, we can address serious problems that exist with cancer surgery today and make sure there are no cancer cells left behind during surgery," said study leader Viktor Gruev, an Illinois professor of electrical and computer engineering and of the Carle Illinois College of Medicine. "This technology is more sensitive, more accurate, much smaller and lower-cost than currently available instruments that are FDA-approved to detect these signals."
Many surgeons rely on sight and touch to find cancerous tissue during surgery, Gruev said. Large hospitals or cancer treatment centers may also use experimental near-infrared fluorescent agents that bind to tumors so that the surgeons can see them on specialized displays.
However, these machines are costly, making them difficult for smaller hospitals to procure; very large, making them difficult to fit into an operating suite and integrate smoothly into surgery; and require the lights to be dimmed so that the instruments can pick up the weak fluorescent signal, making it difficult for the surgeons to see.
"Ninety-five percent of hospitals in the United States have small operating rooms. No matter how good the technology is, if it's too big, it can't enter the surgical suite," said Missael Garcia, a postdoctoral researcher at Illinois and the first author of the paper. "It's a very busy place during the surgery, so rolling in an instrument as big as a table just isn't going to work."
The morpho butterfly's eye has specialized nanostructures that allow it to see multispectral images, including near-infrared. Gruev's team built its camera with the same kinds of nanostructures, creating a small camera that can simultaneously register regular color images and near-infrared signals without needing to dim the room lights.
To make it easy for a surgeon to use, the researchers integrated the camera with surgical goggles.
"The surgeon puts on the goggles that have integrated our bio-inspired camera technology, and it will protect their eyes and at the same time project the fluorescent information whenever they want it," said Gruev, who also is affiliated with the Beckman Institute for Advanced Science and Technology at Illinois. "The goggles are also incredibly low-cost. We anticipate it to cost around $200, compared with $20,000 for the cheapest FDA-approved instrument."
Gruev's group partnered with surgeons at Washington University to test the camera in mice and in humans. The camera was able to find breast-cancer tumors in mice, using a near-infrared fluorescent dye that binds specifically to the type of breast cancer the mice had. Since the camera can pick up signals beneath the surface of the tissue, the surgeons could even locate tumor sites through the skin.
"We could image before the incision and identify the potential points of interest to minimize the incision," Garcia said.
They also tested the camera for finding sentinel lymph nodes in human patients with breast cancer. Doctors need to find and biopsy or remove all the lymph nodes surrounding a tumor to see if the cancer has spread, Gruev said. Doctors use dyes to make the lymph nodes easier to see. In the study, the surgeons used a common green dye that also happens to emit an infrared signal.
They compared how well the physicians could identify the lymph nodes in a patient with breast cancer by looking for green color by eye, and then looking for the infrared signal using the butterfly's-eye camera.
"Our technology is much quicker because one of the advantages is imaging deeper in the tissue," Gruev said. "Sometimes when they're looking for green coloration, they're looking for a while because the nodes are below the surface. With the fluorescence, you can see through the skin or the tissue and identify them much quicker."
The camera also found lymph nodes in two patients that the surgeons did not see visually - and the nodes turned out to be cancerous.
"I would love to see green fluorescence to become the standard for lymph node mapping. It has a huge merit, compared with what's currently being done to locate lymph nodes," Gruev said.
Next, the researchers are working to integrate their camera with endoscopic camera systems. They also have filed a for a patent on the butterfly's-eye camera technology.
Missael Garcia, Christopher Edmiston, Timothy York, Radoslav Marinov, Suman Mondal, Nan Zhu, Gail P Sudlow, Walter J Akers, Julie Margenthaler, Samuel Achilefu, Rongguang Liang, Mohamed A. Zayed, Marta Y. Pepino, Viktor Gruev.
Bio-inspired imager improves sensitivity in near-infrared fluorescence image-guided surgery.
Optica Vol. 5, Issue 4, pp. 413-422 (2018). doi: 10.1364/OPTICA.5.000413.