In dermatology the reflexes of vasoconstriction and vasodilation are known as important mechanisms of thermoregulation of the inner body. Imaging the physiology of microvasculature of the skin with high spatial resolution in three dimensions while reacting to changes in temperature is crucial for understanding the complex processes of vasodynamics, which result in constriction and dilation of vessels. However, previous studies using Laser-Doppler flowmetry and -imaging could not provide reliable angiographic images which allow to quantify changes in blood vessel diameter. Here, we report a different approach for angiographic imaging of microvasculature of a anaesthetized rodent model using speckle variance optical coherence tomography (svOCT) during and after localized cooling. Therefore a commercial OCT with a center wavelength of 1.3 μm and a spatial resolution of 13µm was used in combination with a custom built cooling device to image such reflexes at the mouse ear pinna and dorsal skinfold. Cooling was applied in steps of 2−5◦ C starting at the baseline temperature of 27◦ C down to −10◦ C.
To our surprise and in contrast to the general opinion in literature, we were able to observe that the majority of vessels with a diameter larger than 20 μm maintain perfused with a constant diameter when the tissue is cooled from baseline to subzero temperatures. However, vasoconstriction was observed very rarely and only in veins, which led to their occlusion. The results of this experiment lead us to reconsider essential aspects of previous understanding of temperature-induced vasodynamics in cutaneous microvasculature.
Malte Casper, Hinnerk Schulz-Hildebrandt, Michael Evers, Cuc Nguyen, Reginald Birngruber, Gereon Hüttmann, and Dieter Manstein, "Imaging cold-induced vasodynamic behaviour in skin using OCT for microangiography (Conference Presentation)," Proc. SPIE 10037, Photonics in Dermatology and Plastic Surgery, 100370S (Presented at SPIE BiOS: January 29, 2017; Published: 19 April 2017); https://doi.org/10.1117/12.2251485.5369935384001.
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