SPECTRAL IMAGING/BIOINSTRUMENTATION: Calibrating hyperspectral imaging for biomedical applications

Normally, a microarrayer—so named because it is capable of laying down hundreds of tiny sample droplets in specific places on a microscope slide's surface—creates DNA arrays for genetic research. But a team of researchers at the National Institute of Standards and Technology (NIST) has programmed the tool to select chemicals of different hues and lay them down on the slide. The results can be used to calibrate hyperspectral imaging (HSI) devices and image analysis algorithms for medical application.¹

While many visual surveying methods can scan only for a single color, HSI can distinguish the full color spectrum in each pixel, and thus perceive the unique color "signatures" of individual objects. Well-calibrated HSI sensors have been helpful in discerning problems from diseases in coral reefs to pollution in the atmosphere. Because diseased tissues and cells also have distinct spectra, scientists are exploring medical applications, too. For instance the NIST effort could allow a surgeon to look for cells with a specific chemical makeup, as determined by color.

"Scientists and engineers can create a custom slide with the exact colors representing the chemical makeup they want the HSI devices to detect," says NIST physicist Jeeseong Hwang, who explains that any time you use a machine to scan for something, you must be sure it is looking for what you want, and that the image analysis algorithm extracts the correct color information from a complex data set. His team developed a way to calibrate an HSI device and to test its algorithm. "It could be a good way to make sure the HSI devices for medical imaging perform correctly so that surgeons are able to see all of a tumor or diseased tissue when operating on a patient."

This work is part of a larger effort to evaluate and validate optical medical imaging devices, led by NIST. The issue of Biomedical Optics Express in which the team's findings appear is the output of a recent NIST-supported international workshop on the topic.¹

1. M.L. Clarke et al., Biomed. Opt. Exp., 3, 6, 1291-1299 (2012).