  Optical coherence tomography angiography (Angio-OCT), mainly based on the
temporal dynamics of OCT scattering signals, has found a range of potential
applications in clinical and scientific research. Based on the model of random
phasor sums, temporal statistics of the complex-valued OCT signals are
mathematically described. Statistical distributions of the amplitude
differential and complex differential Angio-OCT signals are derived. The
theories are validated through the flow phantom and live animal experiments.
Using the model developed, the origin of the motion contrast in Angio-OCT is
mathematically explained, and the implications in the improvement of motion
contrast are further discussed, including threshold determination and its
residual classification error, averaging method, and scanning protocol. The
proposed mathematical model of Angio-OCT signals can aid in the optimal design
of the system and associated algorithms.
