Quantification of Skin Adaptation to Lower-Limb Prosthesis Use Through Optical Coherence Tomography Angiography and Thermal Imaging: A Review

Skin breakdown occurs commonly within patients with lower-limb prostheses where the current clinical practice to diagnose skin breakdown is visual inspection by a clinician. Thermal imaging and optical coherence tomography angiography (OCT-A) have been proposed as early detection methods for skin breakdown and hold great promise. OCT-A is a noninvasive imaging modality that outputs a near-infrared optical signal and captures the reflective depth signal. The recorded transient behavior of the vessel area density (VAD), after repetitive dermal loading conditions, has been correlated to skin breakdown. Thermal imaging tracks the temperature profile of the skin surface after repetitive loading conditions and utilizes the temperature time-to-peak (TTP) as a metric of dermal health like VAD. Both methods are sensitive to imaging artifacts, and current resolutions are presented in this work, along with a discussion of the need to standardize data collection and advance image processing methods. Current approaches typically rely on thresholding that produces varying results based on user-selected limits followed by smoothing without any basis of the underlying physics. This review paper presents a need for a constitutive expression that captures the expected physics, thereby strengthening confidence in the use of either thermography or OCT-A, and enabling true clinical applications to aid patient health.