Computationally efficient model of OCT scan formation by focused beams and its usage to demonstrate a novel principle of OCT-angiography

In this paper, we present a computationally highly efficient full-wave model of optical coherence tomography (OCT)-scan formation by focused beams in spectral-domain OCT. Similarly to some previous models, it is based on the summation of fields scattered by discrete sub-resolution scatterers, and enables one to account for the axial and lateral inhomogeneity of the illuminating Gaussian beam. The main feature ensuring the high computational efficiency of the described model is that, rather than numerical integration of the scattered signal over the receiving aperture, we apply an analytical description of both the illuminating-beam focusing and the collection of the scattered signals over the receiving aperture. Elimination of numerical integration over the receiving aperture increases the overall computation speed by a factor of similar to 10(3). This is of key importance in terms of the practical feasibility of simulations of 3D OCT data volumes for large amounts (similar to 10(5)-10(7)) of scatterers, corresponding to realistic densities of cells in biological tissues. We demonstrate the model's possibilities by simulating the digital refocusing of strongly focused OCT beams in the presence moving scatterers, thereby presenting a novel principle of contrast-agent-free visualization of scatterer flows, with velocities typical of blood microcirculation.