Longer wavelengths in the near-infrared range may offer a "golden window" for noninvasive but deep imaging of brain and breast tissue, City College of New York researchers have proposed. Current one- and two-photon fluorescence imaging techniques for deep brain imaging use the "optical window I" near-infrared (NIR) wavelength range, 650 to 950 nm. Theoretical and experimental work led by CCNY research associate Lingyan Shi points to three new optical windows at longer NIR wavelengths that experience reduced scattering in biological tissue. Optical window III, from 1600 to 1880 nm, showed the greatest reduction in scattering and minimal absorption. Longer NIR wavelengths have been overlooked in bioimaging research due to a lack of suitable detectors and light sources, Shi's team said. The research was published in the Journal of Biophotonics (doi: 10.1002/jbio.201500192). The performance of light in near-infrared optical windows I, II, III and IV is compared at various brain tissue thicknesses. Optical window III, from 1600 to 1870 nm, showed the greatest transmittance and least absorption. Courtesy of Shi et al.