Application of a wavelength-swept laser for spectrally resolved wide-field near-infrared fluorescence imaging

Abstract

We propose the proof-of-concept of a novel method for wide-field spectrally resolved near-infrared fluorescence (NIRF) imaging using a wavelength-swept laser. The performance of our method is evaluated on a biotissue-like phantom bearing two inclusions, one filled with indocyanine green (ICG) dissolved in distilled water and the second one in dimethyl sulfoxide (DMSO). A near-infrared wavelength-swept laser covering wavelengths around the peak absorption of ICG was used. The difference in the absorption spectra of these two ICG solutions gives rise to an additional spectral contrast. The distinction between the emitted fluorescence light from the two different solutions is performed using a principal component analysis (PCA)-based method. Results show that the two different ICG solutions were successfully resolved using this approach. This technique can be a powerful method to simultaneously spatio-spectrally image multiple near-infrared fluorescence agents.

Monitoring Distribution of the Therapeutic Agent Dimethyl Sulfoxide via Solvatochromic Shift of Albumin-Bound Indocyanine Green

“…While its superior spectral resolution is a major advantage for this application, the HER-NIRF technique also provides a much higher signal-to-noise ratio by measuring the whole fluorescence emission spectrum as opposed to conventional systems utilizing multiple or variable bandpass filters at the detection site. This will be important, particularly for the tomographic HER-NIRF application, where speed is important [ 25 , 32 , 33 , 34 ]. For in vivo applications that require higher power, optical amplifiers can be utilized to amplify the signal output of the wavelength-swept source.…”

“…In addition, expensive high-speed electronics are necessary to measure the time domain or frequency domain signals. We previously developed a novel hyperspectral excitation-resolved near-infrared fluorescence imaging system (HER-NIRF) based on a continuous-wave wavelength-swept laser [ 25 ]. Based on a semiconductor optical amplifier and a wavelength selector consisting of a holographic transmission grating, a reflection mirror, and a Galvo-scanner mirror, this laser source can provide any wavelength between 784 and 805 nm, a range that is particularly optimal for the ICG absorption peak.…”