Comparing multi- and single-exposure speckle contrast optical spectroscopy methods as estimators of blood flow in the diffuse regime

SignificanceSpeckle contrast optical spectroscopy (SCOS) and speckle plethysmography (SPG) are increasingly used to measure deep tissue blood flow from tissues. However these methods derive flow from measurements at a single exposure duration, which could introduce errors due to inefficient choice of a single integration time, changes in speckle averaging factors (β), and noise.AimThe aims are to compare and evaluate the robustness of single- and multi-exposure speckle contrast methods in estimating blood flow changes under experimental conditions such as β mismatch, noise, and pulsatile flow.ApproachSpeckle visibility was simulated at 10,000 logarithmically spaced exposure durations (0.01 to 10 ms), incorporating ±5 to 15% noise, using a semi-infinite diffusion model at different physiologically relevant steady state and pulsatile flow rates. Speckle visibility was used to estimate blood flow changes using both the multi-exposure approach (non-linear fitting of the full curve) and conventional single exposure approach at 0.1, 1, and 5 ms durations (SCOS, SPG, and look-up-table), under different noise conditions and mismatches in β.ResultsMulti-exposure speckle imaging (MESI) maintained