Near-infrared Fluorescence

Light in the near-infrared spectrum can travel through biological tissues with relatively low absorption and autofluorescence. This optical behavior helps fluorescent signals remain distinguishable from background tissue signals, producing higher-contrast images than would be possible when tissue properties obscure the emission. The resulting contrast supports visualization of labeled structures during diagnostic or image-guided medical procedures.

Near-infrared fluorophores first absorb excitation light and then emit light at a longer wavelength. A sensitive camera detects this emitted signal and converts it into an image of the labeled tissue, vessel, or molecule. The separation between excitation and emission helps the imaging system identify fluorescence associated with the target rather than simply recording the illumination light.

Image contrast depends on how effectively near-infrared light travels through tissue and how strongly background tissue contributes autofluorescence. Relatively low absorption and low autofluorescence in this spectral region help preserve the signal from the fluorophore. When the emitted fluorescence is sufficiently distinct from background, labeled anatomical structures or molecular targets become easier to identify in real time.

A procedure uses a near-infrared fluorophore to label the tissue, vessel, or molecule of interest, followed by illumination with the appropriate excitation light. A sensitive camera captures the resulting longer-wavelength emission and displays it as a real-time image. Clinicians can then use the fluorescent contrast alongside the operative or diagnostic view to identify the labeled target.

Near-infrared fluorescence can support surgical guidance, vascular imaging, lymphatic imaging, tumor localization, and assessment of tissue perfusion. These applications use fluorescent contrast to make relevant structures or functional tissue information visible during medical evaluation or intervention. Because the signal is captured in real time, the method can provide immediate visual guidance rather than only a later image for review.

The method adds optical contrast from labeled tissues, vessels, or molecules to information obtained through conventional imaging. Its use of near-infrared light does not involve ionizing radiation, while real-time fluorescence can assist diagnosis and image-guided procedures. Rather than replacing established imaging approaches, it provides a complementary view that may help improve localization and procedural precision.