Note that concentrations are relative to the volume of the investigated region of interest. For the present purposes the source-detector geometrical configuration is the same for all the instruments and is schematically represented in Fig. 1. The bibliographic references appearing here are technical references.
PPG photoplethysmography, NIRS near infrared spectroscopy, DCS diffuse correlation spectroscopy, IMS intensity modulated spectroscopy, TRS time resolved spectroscopy, LDF laser-Doppler flowmetry, LED light emitting diode, CW continuous wave, IM intensity modulated, DTOF distribution of time-of-flight, BF mean blood flow, ΔBF change in BF, Hb deoxy-hemoglobin concentration, HbO2 oxy-hemoglobin concentration, Δ[Hb change in Hb, Δ]HbO2, change in HbO2, % SO2 blood oxygen saturation, BS mean blood speed, #rbc number moving red blood cells, PMT photo-multiplier tube, APD avalanche photodetector, SPD single-photon detector, a.u. arbitrary units