Impact of the β correction factor on the accuracy of speckle contrast imaging measurements.

Laser speckle imaging (LSI) is a non-invasive technique for quantifying superficial blood flow based on speckle contrast analysis. A critical factor influencing blood flow calculations is the β coefficient, which accounts for system-specific parameters such as speckle-to-pixel size ratio and light polarization. While β is often assumed based on the system's settings, this simplification introduces variability and error in flow quantification, limiting reproducibility and cross-system comparisons. In this study, we present a β-correction approach that uses static phantom measurements to empirically determine β and apply it to correct speckle flow index (SFI) values. We validate this method across three experimental conditions (varying detector polarization, speckle-to-pixel size ratios, and different LSI systems) using both in vitro and in vivo data. Our results demonstrate that β-correction significantly reduces intra-system and day-to-day measurement variability and partially improves inter-system consistency, particularly at low flow speeds. This method enhances LSI reliability for longitudinal clinical monitoring within individual systems by reducing day-to-day measurement variability. While β-correction provides partial improvement with lower coefficients of variation for inter-system consistency at low flow speeds, its primary value lies in standardizing repeated measurements over time.