Fluorescence Imaging of DMDG-ICG Across NIR-I and NIR-II Windows Using a Single-Camera System

Near-infrared (NIR) imaging, including NIR-I (800-1000 nm) and NIR-II (1000-1700 nm), has been primarily evaluated using separate cameras with different detectors, limiting comparison. We investigated whether using a single-camera system capable of both NIR-I and NIR-II acquisition, NIR-II improves spatial resolution and contrast-to-noise ratio (<i>CNR</i>) for nanoparticle-based imaging. Dual-mode, dual-Gd ICG (DMDG-ICG) nanoparticles were characterized for absorption and fluorescence. A custom NIR imaging system using a single InGaAs camera enabled visualizing both NIR-I and -II windows. In vitro, capillary tubes containing nanoparticles in water, in tissue-mimicking Intralipid, or covered with mouse skin were imaged, and full-width-half maximum (FWHM) and <i>CNR</i> were measured. In vivo, the mouse femoral artery was imaged after IV nanoparticle delivery. DMDG-ICG showed strong fluorescence at both NIR-I and NIR-II. Scatter greater at NIR-I than NIR-II increased with depth and tissue layers. FWHM was lower and <i>CNR</i> higher at NIR-II versus NIR-I for up to 10 mm depth (<i>p</i> < 0.05, <i>n</i> = 3) in Intralipid. In vivo, femoral artery <i>CNR</i> was also higher at NIR-II (<i>p</i> < 0.05, <i>n</i> = 3). Using a single-camera system allowing direct comparison, NIR-II imaging provided greater penetration, spatial resolution, and <i>CNR</i> compared to NIR-I. The findings support the utility of NIR-II for vascular and molecular imaging applications.