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Table 1 Optical instruments utilized to investigate bone blood flow in humans

From: Near-infrared photons: a non-invasive probe for studying bone blood flow regulation in humans

Instrument name Possible source types Possible number of light wavelengths Light source intensity Detected parameters for light (possible detector types) Measured physiological parameters
PPG [32] LED 1 Constant Intensity (PMT, APD) ΔBF (a.u.)
NIRS [33] LED, CW laser, white light 1, 2, 3, …, to continuous Constant Intensity (PMT, APD) Hb, HbO2, ΔHb, ΔHbO2, (a.u.) and %SO2
DCS [34] CW laser 1 Constant Temporal correlation (SPD) BF (cm2 s −1)
IMS [35] IM laser 2, 3, … Sinusoidal modulation Intensity and intensity phase shifts (PMT, APD) Hb, HbO2, (μM) and %SO2
TRS [36] Pulsed laser 2, 3, … Pulsed Photon DTOF (SPD) Hb, HbO2, (μM) and %SO2
LDF [37] CW laser 1 Constant Doppler frequency shift (PMT, APD, SPD) BF, BS, #rbc (a.u.)
  1. 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.
  2. 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, Δ BF change in BF, Hb deoxy-hemoglobin concentration, H b O 2 oxy-hemoglobin concentration, Δ[H b change in Hb, Δ]H b O 2, change in H b O 2, % S O 2 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