An in-house-built clinical prototype OCT system (Figure 1A) was used in this study. The system was similar to that published in (21,22) but re-configured for clinical research in dermatology. Briefly, the system was equipped with a 200 kHz swept laser source (SL1310V1-10048, Thorlabs Inc.) with a central wavelength of 1,310 nm (infrared range) and spectral bandwidth of 100 nm to provide an axial resolution of ~8 µm in tissue (~11 µm in air). The sample arm was configured as a hand-held probe with a 6.5", 1080p display monitor, sample spacer, and disposable contact unit. A 5× objective lens focused the light source into a beam spot with an incident power of 5 mW, whilst a paired galvo scanner was used to scan the probe beam over the skin to form raster sampling patterns consisting of fast (x-axis) and slow (y-axis) axes.

Images showing the prototype OCT system alongside a schematic of data processing. (A) The prototype OCT system capable of OCTA data acquisition; (B) original structural cross-section B-frame images; (C) attenuation correction cross-section B-frame images; (D) 3D structure image. Red lines highlight graft layer boundaries (graft layer further highlighted with a red arrow) and green lines highlight integration layer boundaries (integration layer further highlighted with a green arrow). Layer segmentation was carried out using these lines; (E) vascular cross-section B-frame images; (F) original en face projection of 3D blood vessels; (G) binarized vascular image used for the quantification of vascular area density; (H) skeletonized vascular image used for the quantification of vascular diameter. Scale bar represents 1 mm.