Miniaturized Blood-Flow Sensing Using Laser Speckle Imaging

In biomedical applications, laser speckle imaging (LSI) has traditionally been a benchtop technology, widely utilized as a noncontact method for generating high-resolution, real-time maps of tissue perfusion. We present the evolution of this technology from the bench to a miniaturized, wearable LSI device. Leveraging advancements in laser source and camera sensor technology, our wearable LSI system captures real-time blood flow dynamics—termed speckleplethysmography (SPG)—with a signal-to-noise ratio 40 times greater than that of traditional photoplethysmography (PPG), the foundational signal in pulse oximetry. Notably, the SPG signal remains stable under motion and temperature fluctuations, maintaining waveform integrity where PPG typically deteriorates. We have further enhanced this technology by integrating LSI with spatially-resolved diffuse reflectance spectroscopy (srDRS), creating a coherent spatial imaging (CSI) system that enables continuous monitoring of tissue composition and oxygenation in both clinical and field-deployable settings. This combined CSI platform provides an affordable, compact alternative to conventional bulky systems, delivering assessments of tissue absorption, scattering, hemoglobin concentration, and blood flow with high temporal resolution. Validation studies demonstrate strong agreement between CSI and gold-standard technologies like spatial frequency domain imaging (SFDI) and diffuse optical spectroscopy for tissue absorption and scattering measurements. This CSI sensor represents an advancement in physiological and trauma management, offering enhanced diagnostics and actionable insights in clinical and critical-care environments.