Assessing the Health and Functionality of the Microcirculation Using Thermal Imaging

The microcirculation, composed of vessels below 100 μm in diameter, sustains tissue perfusion and metabolic exchange. Its dysfunction is increasingly implicated in chronic, inflammatory, and thrombotic disorders such as diabetes, sepsis, cardiovascular disease, and Long COVID. Accurate, noninvasive assessment of microvascular health is therefore clinically significant. Infrared thermal imaging provides a rapid, contact-free, and physiologically coherent means of visualizing temperature distributions that reflect underlying blood flow. Because thermal gradients directly correspond to perfusion heterogeneity, this approach offers an interpretable surrogate for assessing microvascular function. Here, we review the physical principles of thermal imaging, summarize its application to the peripheral circulation, and compare it with established modalities including nailfold capillaroscopy and laser-based techniques. We also outline its utility across diverse pathologies associated with fibrinaloid microclot complexes and endothelial injury. Thermal imaging thus emerges as an inexpensive/scalable tool for evaluating microcirculatory dysfunction in both research and (where approved) in clinical settings.