Figure 5.

PS-OCT imaging of a fingertip DU, with overlying scab/crust. (a) Clinical photograph (red box represents imaging boundaries, red curved line the edge of the lesion crust). (b) OCT surface profile scan, of site within the red box in (a), showing the curvature of the finger and affected area, surface at the DU is raised due to crust. (c) 2D slice of OCT 3D scan, along the green line (in (a) and (b)), showing both surface and subsurface tissue at the DU site (imaging through the crust (marked with white arrow) and epidermis (black arrow)). (d) OCT scan showing ‘birefringence’ of the collagen indicating both the crust and tissue surface boundaries (same site as (c)). Concave surface of the skin (black arrow) at the ulcer site is visible in (c) despite imaging through the crust (white arrow). Images courtesy of Lewis Smith.