Capillary Refill—The Key to Assessing Dermal Capillary Capacity and Pathology in Optical Coherence Tomography Angiography

Abstract

Background/Objectives Standard optical coherence tomography angiography (OCTA) has been limited to imaging blood vessels actively undergoing perfusion, providing a temporary picture of surface microvasculature. Capillary perfusion in the skin is dynamic and changes in response to the surrounding tissue's respiratory, nutritional, and thermoregulatory needs. Hence, OCTA often represents a given perfusion state without depicting the actual extent of the vascular network. Here we present a method for obtaining a more accurate anatomic representation of the surface capillary network in human skin using OCTA, along with proposing a new parameter, the Relative Capillary Capacity (RCC), a quantifiable proxy for assessing capillary dilation potential and permeability. Methods OCTA images were captured at baseline and after compression of the skin. Baseline images display ambient capillary perfusion, while images taken upon capillary refill display the network of existing capillaries at full capacity. An optimization‐based automated vessel segmentation method was used to automatically analyze and compare OCTA image sequences obtained from two volunteers. RCC was then compared with visual impressions of capillary viability. Results Our OCTA imaging sequence provides a method for mapping cutaneous capillary networks independent of ambient perfusion. Differences between baseline and refill images clearly demonstrate the shortcomings of standard OCTA imaging and produce the RCC biometric as a quantifiable proxy for assessing capillary dilation potential and permeability. Conclusion Future dermatological OCTA diagnostic studies should implement the Capillary Refill Methods over standard imaging techniques and further explore the relevance of RCC to differential diagnosis and dermatopathology. Lasers Surg. Med. © The Authors. Lasers in Surgery and Medicine published by Wiley Periodicals, Inc.

Assessing the impact of aging and blood pressure on dermal microvasculature by reactive hyperemia optical coherence tomography angiography

“…All data sets were deidentified and automatically segmented vessels (Fig. 2 ) were analyzed by various quantitative metrics described in detail in earlier works 17 , 32 . In summary, the vessel density (VD) is based on the area of segmented vessels (red pixels) as a percentage of the entire image (Fig.…”

“…Comparing quantitative values of the skin’s baseline perfusion of conventional OCT-A and the peak hyperemia perfusion of RH-OCT-A allowed for the determination of the relative capillary capacity: The relative capillary capacity (RCC) metric is a ratio that is expressed as a percentage change and it should be seen as a statistical convenience that permits information to be collected from multiple variables. While the relative capillary capacity is not a physiological metric it could help as an indicative value to quantify dynamic vascular changes in response to capillary wall stiffness, vessel permeability, and other factors 17 . MATLAB code and example data are archived at https://github.com/MichaWangEvers/Vessel-Segmentation .…”

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“…Such complexity signifies that full characterization of changes in vessel morphology will require multiple metrics. We chose eight metrics to comprehensively characterize microvascular network architecture based on an extensive qualitative review of the literature, balancing coverage and overlap of characteristics [ 13 , 44 – 48 ]. These metrics allow users to obtain comprehensive information about the microvasculature [ 49 ].…”

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