Felh series

A multispectral SWIR fluorescence imaging system was designed and constructed (Fig. 2). Briefly, tissue is illuminated by a 785-nm fiber-coupled laser (BWF-1-785/55371, B&W Tek) dispersed onto the sample using a ground glass diffuser (DG10-220-MD, Thorlabs, Germany). SWIR fluorescence emission from the sample is collected by a highly sensitive InGaAs camera [ $\mathrm{QE}>80\%$ 950 to 1600 nm, NIRvana 640, Teledyne Princeton Instruments Fig. 2(b)] coupled to a SWIR lens ( $f=16\mathrm{mm}$ , F/1.4, Navitar, Canada). Fluorescence light is sequentially filtered using a six-position filter wheel (LTFW6, Thorlabs, Germany) through six long-pass filters with cut-off wavelengths of 850, 950, 1050, 1150, 1250, and 1350 nm [FELH series, Thorlabs, Germany, Fig. 2(b)]. The system was mounted inside a light-tight enclosure to remove background light. The camera was cooled to $-80°\mathrm{C}$ to reduce thermal noise.

A novel system was designed and constructed (Fig. 1). Briefly, tissue is illuminated by a 785-nm fiber-coupled laser (BWF-1–785/55371, B&W Tek) dispersed onto the sample using a ground glass diffuser (DG10–220-MD, Thorlabs). SWIR fluorescence emission from the sample is collected by a highly sensitive InGaAs camera (QE > 80% 950–1,600 nm, NIRvana 640, Teledyne Princeton Instruments) coupled to a SWIR lens (f = 16 mm, F/1.4, Navitar). Fluorescence light is sequentially filtered using a 6-position filter wheel (LTFW6, Thorlabs) through 6 long-pass filters with cut-off wavelengths of 850, 950, 1,050, 1,150, 1,250, and 1,350 nm (FELH series, Thorlabs). The system was mounted inside a light-tight enclosure to remove background light. The camera was cooled to −80°C to reduce thermal noise. Images were captured using LightField (Teledyne Princeton Instruments) and saved as 16-bit TIFs for analysis.