In vivo photoacoustic assessment of the oxygen saturation changes in the human radial artery: a preliminary study associated with age

Significance: We demonstrate the potential of probing the [Formula: see text] change under blood flow in vivo using photoacoustic (PA) imaging and sheds light on the complex relationship between RBC aggregation and oxygen delivery. Aim: To conduct in vivo assessments of the [Formula: see text] in the radial artery of healthy volunteers and simultaneously probe the relation between the [Formula: see text] and hemodynamic behavior such as red blood cell (RBC) aggregation. Approach: The effects of PA-based measurements of blood hemodynamics were studied as a function of the subjects’ age (20s, 30s, and 40s). The pulsatile blood flow in the human radial artery of 12 healthy subjects was imaged in the 700 to 900 nm optical wavelength range using a linear array-based PA system. Results: The PA power when blood velocity is minimum ([Formula: see text]) was larger than the one attained at maximum blood velocity ([Formula: see text]), consistent with predictions based on the cyclical variation of RBC aggregation during pulsatile flow. The difference between [Formula: see text] and [Formula: see text] at 800 nm ([Formula: see text]) increased with age (1.7, 2.2, and 2.6 dB for age group of 20s, 30s, and 40s, respectively). The [Formula: see text] computed from [Formula: see text] was larger than the one from [Formula: see text]. Conclusions: The [Formula: see text] increased with participant age. The [Formula: see text] metric could be a surrogate of noninvasively monitoring the age-induced changes in RBC aggregation. The [Formula: see text] change during a cycle of pulsatile blood flow also increased with age, demonstrating that RBC aggregation can affect the [Formula: see text] change.