Fiber-optic point measurements were acquired with a measurement setup [shown in Fig. 2(b) ] including a broadband light source, a spectrometer for the visual wavelength region (Andor Technology DU420A-BRDD), and a spectrometer for the near-infrared region (Andor Technology, DU492A-1.7). A fiber-optic probe was attached to the measurement setup to measure diffuse reflectance spectra between 400 and 1600 nm [Fig. 2(d) ].18 (link),19 (link) The distance between the illuminating and collecting fiber at the tip of the probe was 1 mm. Before measuring, the setup was calibrated by acquiring a white reference measurement of Spectralon® (SRT-99-100, Labsphere, Inc., Northern Sutton, New Hampshire) in a calibration cap.
To acquire a DRS measurement, the probe was brought in contact with the tissue. During the probe measurements, a custom-made grid with holes [consisting of two pieces and shown inFig. 2(c) ] was placed on top of the tissue to gently fixate the tissue in the cassette and allow correlation between the measurement locations and H&E section afterward. The grid was 3-D printed and transparent. In addition, the grid stabilized the probe while ensuring contact between the probe and the tissue and restraining it from moving during measurements.
To acquire a DRS measurement, the probe was brought in contact with the tissue. During the probe measurements, a custom-made grid with holes [consisting of two pieces and shown in
