TY - DATA T1 - Self-Calibration Phenomenon for Near-Infrared Clinical Measurements: Theory, Simulation, and Experiments PY - 2018/03/08 AU - Idit Feder AU - Hamootal Duadi AU - Ruchira Chakraborty AU - Dror Fixler UR - https://acs.figshare.com/articles/media/Self-Calibration_Phenomenon_for_Near-Infrared_Clinical_Measurements_Theory_Simulation_and_Experiments/5965123 DO - 10.1021/acsomega.8b00018.s001 L4 - https://ndownloader.figshare.com/files/10689202 KW - Near-Infrared Clinical Measurements KW - method KW - oxygen saturation determination KW - measurement KW - semi-infinite tissue geometries KW - IPL point KW - NIR N2 - An irradiated turbid medium scatters the light in accordance to its optical properties. Near-infrared (NIR) clinical methods, which are based on spectral-dependent absorption, suffer from an inherent error due to spectral-dependent scattering. We present here a unique spatial point, that is, iso-pathlength (IPL) point, on the surface of a tissue at which the intensity of re-emitted light remains constant. This scattering-indifferent point depends solely on the medium geometry. On the basis of this natural phenomenon, we suggest a novel optical method for self-calibrated clinical measurements. We found that the IPL point exists in both cylindrical and semi-infinite tissue geometries (Supporting Information, Video file). Finally, in vivo human finger and mice measurements are used to validate the crossing point between the intensity profiles of two wavelengths. Hence, measurements at the IPL point yield an accurate absorption assessment while eliminating the scattering dependence. This finding can be useful for oxygen saturation determination, NIR spectroscopy, photoplethysmography measurements, and a wide range of optical sensing methods for physiological aims. ER -