Imaging the vasculature of a beating heart by dynamic speckle: the challenge of a quasiperiodic motion.

The spatial and temporal evolution of the field backscattered by a beating heart while illuminated with a coherent light reveals its macro- and microvascularization in real time. To perform these vascularization images, we use a recently published method of laser speckle imaging, based on the selective detection of spatially depolarized speckle field that is mainly generated by multiple scattering. We consider the calculation of the speckle contrast, by a spatial or temporal estimation. We show that the signal-to-noise ratio of the observed vascular structure can be noticeably increased by a postprocessing method implying the calculation of a motion field that allows the selection of similar frames extracted from different heartbeat periods. This later optimization reveals vascular microstructures with a spatial resolution of the order of 100 µ m .

Imaging of the skin microvascularization using spatially depolarized dynamic speckle.

SIGNIFICANCE: We propose a technique devoted to real-time high-resolution imaging of skin microvascularization. AIM: The process utilizes the temporal variation of the spatially depolarized optical speckle field generated by moving red blood cells when illuminated with fully polarized coherent light. APPROACH: Polarimetric filtering prevents the contribution of surface scattering from reaching the camera and thus favors the detection of multiscattered photons from the deeper layers of the skin. RESULTS: Full-field images reveal the microvasculature with a spatial resolution of 80 µm. The acquisition speed allows for real-time applications. CONCLUSIONS: We demonstrate the ability of this method to determine in 1 s a stable and reliable microvascular activity, enabling numerous clinical applications that require quantitative measurements.