Shot-noise limited phase-sensitive imaging of moving samples by phase-restoring subpixel motion correction in Fourier-domain optical coherence tomography

Abstract

AbstractPhase-sensitive Fourier-domain optical coherence tomography (FD-OCT) enables label-free imaging of cellular movements in vivo with detection sensitivity down to the nanometer scale. Due to this high sensitivity, it is widely employed in various emerging functional imaging modalities such as optoretinography (ORG), optical coherence elastography (OCE), and optical coherence tomography angiography (OCTA). However, achieving shot-noise limited detection sensitivity remains a major challenge for in-vivo measurements where the sample is constantly affected by vascular pulsation, breathing, eye and head motion, and other involuntary movements. Here, we propose a phase-restoring subpixel motion correction (PRSMC) method for post-hoc image registration in FD-OCT. Based on a generalized FD-OCT model, this method enables translational shifts of OCT images by arbitrary displacements while accurately restoring physically meaningful phase components, both with subpixel precision. With the sample movements estimated from averaged Doppler shift or normalized cross-correlation, we reconstructed the OCT images by correcting the axial displacement in the spectrum (k) domain and the lateral displacement in the spatial frequency domain, respectively. We validated our method in simulations, phantom experiments, and in-vivo optoretinogram imaging, where the advantages over conventional approaches for both amplitude stability and phase accuracy were demonstrated. Our approach significantly reduces the motion-induced phase error (MIPE) when imaging moving samples, achieving systematic phase sensitivities close to the shot-noise regime.