Comparative study to analyze the effect of aging on microvascular blood flow by processing laser speckle contrast images when Lorentzian and Gaussian velocity profiles are assumed for moving scatterers

It is well known that microcirculation alters with age. These alterations can be evaluated by monitoring microvascular blood flow. Laser speckle contrast imaging (LSCI) is a recent optical imaging modality to monitor microvascular blood flow. From LSCI, the average velocity of microvascular moving scatterers (mainly red blood cells from the microcirculation) can be evaluated when assumptions on the scatterers velocity distribution are made. The objective of this study is twofold: 1) Process experimental LSCI data to compare velocity of red blood cells from the microcirculation when a Lorentzian profile and when a Gaussian profile are assumed. The experimental images that are processed have been recorded in healthy subjects, at rest, during a vascular occlusion and post-occlusive reactive hyperaemia, in two populations: young and aged subjects. 2) Analyze if alterations of microcirculation with age can be evaluated by processing LSCI data. Moreover, the presence of static scatterers (like skin) is taken into account in our work. Our results show that red blood cells velocity values determined when a Lorentzian velocity profile is assumed are lower than the ones determined when a Gaussian velocity profile is assumed, both for the young and the aged subjects. This is true with or without the presence of static scatterers. Furthermore, at rest, during biological zero, and post-occlusive reactive hyperaemia, the velocity of the moving scatterers increases with age. It also increases when the part of static scatterers increases. LSCI is therefore a new imaging modality that can be used to assess alterations of microvascular blood flow with age.