Real-time, macroscopic shortwave infrared Raman imaging for surgical and pre-clinical applications

Optical imaging has transformed biomedical research and clinical practice by revealing tissue identity and function in living organisms and during surgery. In the shortwave infrared (SWIR, 1000-1700 nm), biological tissues exhibit lower scattering and autofluorescence, properties that improve penetration depth and image contrast. Raman scattering imaging is a label-free optical technique that provides chemical information across a wide range of applications, particularly at microscopic and mesoscopic scales. In biological tissues, however, macroscopic Raman imaging has remained challenging because, at visible and near-infrared wavelengths, autofluorescence overwhelms the weak Raman signals. Here we integrate the favorable optical properties of SWIR with the specificity of Raman scattering to establish SWIR Raman imaging for real-time, high-contrast chemical imaging across surgically relevant fields of view. We demonstrate its versatility by monitoring tissue dynamics in living animals, detecting fatty liver disease non-invasively in mice, and identifying calcification and lipids in human atherosclerotic plaques. In surgical settings, SWIR Raman reveals lymph nodes and nerves that are invisible otherwise, providing magnetic-resonance-imaging-like anatomical information directly in the operation field for real-time surgical guidance. SWIR Raman thereby expands the capabilities of optical imaging to applications requiring rapid biochemical identification over large tissue areas and can improve surgical decision-making and patient outcomes.