Rotational Distortion and Compensation in Optical Coherence Tomography with Anisotropic Pixel Resolution

Accurate image registration is essential for eye movement compensation in optical coherence tomography (OCT) and OCT angiography (OCTA). The spatial resolution of an OCT instrument is typically anisotropic, i.e., has different resolutions in the lateral and axial dimensions. When OCT images have anisotropic pixel resolution, residual distortion ([Formula: see text]) and false translation ([Formula: see text]) are always observed after image registration for rotational movement. In this study, [Formula: see text] and [Formula: see text] were quantitively analyzed over different degrees of rotational movement and various lateral and axial pixel resolution ratio ([Formula: see text]) values. The [Formula: see text] and [Formula: see text] provide the evaluation criteria for image registration. The theoretical analysis confirmed that the [Formula: see text] and [Formula: see text] increase significantly with the rotation degree and [Formula: see text]. An image resizing assisting registration (RAR) strategy was proposed for accurate image registration. The performance of direct registration (DR) and RAR for retinal OCT and OCTA images were quantitatively compared. Experimental results confirmed that unnormalized [Formula: see text] causes [Formula: see text] and [Formula: see text]; RAR can effectively improve the performance of OCT and OCTA image registration and distortion compensation.