Clinical system
The clinical system employed a 75 W fiber-coupled xenon short arc light source (SLS205, Thorlabs) as a source of the white light and three spectrometers (AvaSpec-2048-USB2, Avantes) for the collection of spectra at three source-detector separations. The system was assembled on a cart for convenient transportation to the clinic (see Fig. The probe consisted of seven fibers, each with a 100 μm core diameter and NA = 0.22. A single fiber located in the outer ring of the LSS-DRS probe served as the delivery fiber and three fibers positioned at 120 µm, 220 µm and 240 µm center-to-center from the delivery fiber served as the collection fibers. At the proximal end, each collection fiber was coupled to an individual spectrometer channel. In this study the closest (120 μm) and farthest (240 μm) fibers, providing two distinct source-detector separations, were employed for the data analysis. The overall diameter of the probe was 0.9 mm, making it compatible with the 1.2 mm working channel of all currently used cholangioscopy systems (Boston Scientific SpyGlass, Pentax FCP-9P and FCN−15X, Olympus CHF-BP30 and CHF-CB30L/S) and all ERCP catheters.