FOCUS: Flow dynamic and optical property coupled laser speckle imaging for quantitative blood flow mapping

Laser speckle contrast imaging (LSCI) provides label-free, wide-field blood-flow imaging with high spatiotemporal resolution, but its quantitative interpretation remains challenging because the measured speckle contrast is affected by both tissue optical properties and flow dynamics. Here, we present Flow dynamic and Optical property Coupled Laser Speckle Imaging (FOCUS), which integrates LSCI with spatial frequency domain imaging (SFDI) for quantitative blood-flow mapping. FOCUS employs a single laser source, a laser speckle reducer, and a digital micromirror device. This configuration enables switching between high-coherence planar illumination for LSCI and low-coherence structured illumination for SFDI, allowing pixel-wise co-registered measurements at the same wavelength. SFDI is used to recover the absorption coefficient μa and the reduced scattering coefficient μs′, whereas LSCI provides the speckle contrast K. These measurements are incorporated into a correlation–diffusion-based inversion framework to estimate quantitative blood-flow parameters on a pixel-wise basis. To account for different flow regimes, FOCUS considers both Brownian and directed-flow motion models and constructs corresponding dual-dynamics lookup tables. Phantom experiments demonstrate improved repeatability under varying optical properties and flow speeds. In vivo, FOCUS maintains stable perfusion measurements during indocyanine green injection in large vessels. It also sensitively detects flow reduction in the ischemic core of a photothrombotic stroke model. These results demonstrate the feasibility of FOCUS for quantitative laser speckle perfusion imaging with optical-property correction.