Spatio-temporally modulated fluorescence imager for intraoperative nerve identification

Significance: Fluorescence-guided surgery (FGS) based on nerve-labeling agents has the potential to enhance nerve identification during various operational procedures including orthopedic, craniofacial, and otolaryngological surgeries that involve complex and delicate nerve structures. A major challenge in FGS is the adverse impact of strong ambient light, which interferes with weak fluorescence signals, especially at visible wavelengths. Currently, this issue is mitigated by dimming or turning off the operating room (OR) lights during the fluorescence imaging procedure. However, this causes substantial disruption to the surgical workflow and reduces the potential for clinical adoption of FGS technologies. Aim: In this work, we develop a novel intraoperative fluorescence imager that is based on a spatio-temporal modulation (STM) approach to suppress interference from strong OR lights. Approach: The STM technology employed a line-scan imaging scheme that encodes the fluorescence signal into a distinctive spatial frequency within a narrow time window. By applying spatial frequency demodulation and time-gating methods, the imager effectively extracted the fluorescence signals by rejecting temporally constant and spatially uniform background OR lights. Results: human nerve tissue specimens and perfused amputated human limbs further supported the clinical suitability and readiness. Conclusions: This innovative imaging technology enables high-contrast fluorescence visualization of nerve tissue under standard OR lighting and represents a significant step toward practical clinical implementation of FGS for enhanced nerve identification.