Du420a brdd

Measurements were obtained with a system consisting of a broadband tungsten halogen light for illumination and two different spectrometers to record the diffuse reflectance spectra from the tissue. The first spectrometer contained a silicon detector resolving the visual light between 400 and 1100 nm (Andor Technology, DU420A-BRDD), and the second spectrometer contained an InGaAs detector resolving light in the NIR region from 800 to 1700 nm (Andor Technology, DU492A-1.7). 14 (link) The optical fibers guiding the light from the light source toward the tissue and the light reflected from the tissue toward the spectrometers are in contact with the tissue via a handheld probe. Multiple diffuse reflectance spectra were obtained for different distances between source fiber and detector fiber: 0.3, 0.7, 1, and 2 mm (Fig. 1). Different source-detector distances were used to obtain different sampling depths.

Raman spectra were recorded using a custom-built Raman microspectroscopy system, as previously described [22, (link)23] (link). Briefly, this system employed a 150 mW laser with a wavelength of 532 nm (Laser Quantum, Torus), spectrograph (Andor, Shamrock 500) operating with 600 lines/mm grating, and a CCD camera (Andor; DU420A-BR-DD) cooled to -80 °C. A 50× microscope objective (MO), with numerical aperture of 0.8 (Olympus, UMPlanFl), was used to image the spectral irradiance to a 100 μm confocal aperture, which isolates the signal from the cell nucleus, and minimises background noise from the sample substrate, as well as from optical elements in the system [22, (link)23] (link).

The DRS system consists of a Tungsten halogen broadband light source (360 to 2500 nm) with an embedded shutter and two spectrometers. Together, the two spectrometers cover the visible and near-infrared light range; the first spectrometer resolves Journal of Biomedical Optics 106014-2 October 2017 • Vol. 22 (10) light in the visible range 400 to 1100 nm (Andor Technology, DU420ABRDD), whereas the second resolves light in the near-infrared range 900 to 1700 nm (Andor Technology, DU492A-1.7) (Fig. 2). The spectrometers are controlled by custom LabView software (National Instruments) to acquire the data. The DRS system used in this study has been extensively described previously together with the calibration used for the system. 19, (link)20 (link) In all patients, the same probe, shown in Fig. 2, was used to obtain the DRS measurements. The probe consists of three optical fibers with a core diameter of 200 μm. One of the three fibers was used to transport the light from the source to the tissue, whereas the other two were used to transport the light from the tissue to one of both spectrometers. The distance between the two collecting fibers and the delivering fiber is 2 mm. This gives a mean sampling depth of about 2 mm (max 4 mm).