Imaging nerves during surgery without turning down the lights

Avoiding accidental nerve damage is an important concern in many surgical procedures. Nerves can be difficult to distinguish from surrounding tissue, particularly in complex anatomical regions. Fluorescence-guided surgery could make them easier to see by using fluorescent agents that selectively highlight nerve tissue. But there is a practical obstacle: the fluorescence signal can be weak compared with the bright ambient light of an operating room. Surgeons may therefore need to dim or switch off the room lights during fluorescence imaging, interrupting normal surgical workflow.

As reported in Journal of Biomedical Optics, researchers from Physical Sciences Inc. and Dartmouth College recently developed an imaging system designed to overcome this limitation. Their approach separates fluorescence emitted by labeled nerves from the much stronger background illumination, allowing nerve signals to be visualized under standard operating-room lighting.

The problem is especially challenging for fluorescence at visible wavelengths. Light from surgical lamps can reach the camera along with the desired fluorescence, reducing contrast and potentially obscuring the structures being highlighted. Instead of trying simply to block this unwanted light, the researchers developed a way to give the fluorescence signal a recognizable spatial and temporal pattern that distinguishes it from ordinary illumination.

The system uses line-scan imaging, collecting the fluorescence signal from a narrow region at a time. This encodes the fluorescence into a specific spatial frequency and confines its detection to a short time window. Image-processing methods then extract signals matching this pattern while suppressing background light that remains relatively constant over time and uniform across the field of view. The approach combines spatial-frequency processing with precise timing of signal collection.

The researchers tested whether the technique could identify nerves under lighting conditions representative of an operating room. Preliminary studies showed that the imager could detect nerve structures despite the presence of strong ambient illumination. The team then extended the evaluation from live animal models to excised human nerve specimens and perfused amputated human limbs, providing tests in tissue that more closely represents the conditions expected during human surgery.

Across these experiments, the system produced high-contrast fluorescence images of nerve tissue under normal operating-room illumination. The results indicate that spatial and temporal modulation can separate relatively weak nerve fluorescence from a much brighter optical background without requiring the surrounding lights to be turned down.

This distinction is important for translating fluorescence-guided nerve imaging into routine surgical practice. An imaging technology may perform well experimentally but remain difficult to adopt if using it requires surgeons and operating-room staff to repeatedly change their normal working conditions. Allowing fluorescence images to be acquired without altering room lighting removes one such practical barrier.

Further clinical evaluation will be needed to determine how the technique performs during human surgical procedures. Still, the work demonstrates an approach to a broader problem in fluorescence-guided surgery: extracting weak, tissue-specific optical signals in a bright and visually demanding clinical environment. By addressing the imaging environment rather than requiring the environment to accommodate the imaging system, the technique could make fluorescence-based nerve visualization easier to integrate into surgical workflows.

For details, see the original Gold Open Access article by J. Park et al., “Spatio-temporally modulated fluorescence imager for intraoperative nerve identification,” J. Biomed. Opt., 31(10), 106001 (2026), doi: 10.1117/1.JBO.31.10.106001