Based on the first-generation visible NIR-I/NIR-II integrated imaging system, an NIR-II imaging system was developed for better clinical application.16 (link) As shown in Figure 1 , it has the merits of portability, light weight (4 kg), and ease of operation. An InGaAs camera (640×512 pixels, TE4-25; Hengxin, Shenyang, China) cooled to −80°C was utilized to capture images in the NIR-II window. According to the experimental requirements, NIR-II fluorescence signals were able to be extracted by various long-pass filters. For example, were a 1,100 nm image needed, we would fit a 1,100 nm long-pass filter (ThorLabs, Newtown, NJ, USA) to the camera, limiting wavelength <1,100 nm to pass through the lens. A silicon camera (1,920×1,080 pixels, CS2100M; ThorLabs, Newtown, NJ, USA) equipped with a 900 nm short-pass filter was used to acquire images in the NIR-I window. In both NIR-I window and NIR-II window fluorescence imaging, a 785 nm laser (Ningbo Yuanming Laser Technology, Zhejiang, China) beam was exploited to provide uniform illumination extended through a lens on the region of interest (ROI), and the excitation wavelength was filtered away by 800 nm long-pass filters. The facular power density was consistently adjusted to 10–15 mW/cm2 during testing.![]()
NIR-I/II fluorescence imaging system used for in vivo NIR fluorescence imaging in porcine limbs.