BOLD signal Monte Carlo simulations NIRS Public health & preventive medicine RGB imaging Sidestream Darkfield Microscopy (SDF) absorption spectra brain breath-holding broadband diffuse reflectance spectroscopy cytochrome C oxidase diffuse optics dual-slope esophagectomy fluorescence angiography fluorescence imaging frequency-domain near-infrared spectroscopy gastric conduit hemodynamic brain mapping hyperspectral imaging indocyanine green (ICG) intraoperative imaging laser speckle contrast imaging (LSCI) metabolic brain mapping multispectral near-infrared spectroscopy optical coherence tomography (OCT) optical imaging supercontinuum laser tissue optics