A Fast Optical Coherence Tomography based Angiography Projection (FOCTAP) Method on Dermatology Applications

Optical coherence tomography (OCT) based angiography (OCTA) is a non-invasive imaging methodology that can extract the microvasculature networks within the tissue. Real-time OCTA projection can provide a number of advantages for OCTA imaging, e.g., real-time diagnosis, and image-guided treatment/surgery. However, the high computational cost required for real-time OCTA projection is a huge challenge, as the traditional OCTA projection requires Fourier transform and 3D OCTA reconstruction. This study introduces a novel technique, Fast OCTA Projection (FOCTAP), designed to facilitate the creation of en face OCTA projections swiftly and more efficiently. FOCTAP bypasses the need for FFT by directly using the sum of raw OCT interference signals to create en face structural projections, from which the OCTA projection can be extracted using eigen-decomposition. The application of FOCTAP to human palm skin, using a swept-source OCT system, demonstrated significant computational time reduction (at least 16 times) compared to traditional methods. For a conventional data size, FOCTAP took 0.45 seconds to generate one en-face OCTA projection result, substantially quicker than traditional methods using aED (12.48 seconds), bED (7.14 seconds), or wED (1123.38 seconds), on an Intel i9-12900K CPU. FOCTAP maintains processing times under 0.5 seconds, thereby demonstrating a promising potential for real-time OCTA projection.