Noise-Free One-Cardiac-Cycle Oct Videos for Local Assessment of Retinal Tissue Deformation.

The analysis and quantification of retinal tissue biomechanics is important for understanding the pathophysiology of glaucoma. The dynamics of anatomical changes can uncover information that is not available in static Optical Coherence Tomography (OCT) images. However, noise in OCT images hampers detailed analysis of time series with high levels of accuracy. In order to produce good quality videos of the retina, we reduced video acquisitions of approximately thirty seconds to one cardiac cycle by synchronizing the acquisition of OCT images with the measurement of the patient's pulse. After spatial registration of the images, we phase wrapped each measurement using the heart frequency to average the frames of the video which correspond to the same instant in the cardiac cycle. These videos with a duration of a single cycle allow a precise analysis of the movement of the tissues of the retina. Using the proposed workflow on the OCT acquisitions of 15 patients (video length of 30 seconds), the CNR and SNR, which measure signal quality in the images, and the MMI, which measures registration accuracy, all increased significantly. The resulting videos allow local tissue displacement to be seen more clearly and analysed more precisely than with standard image registration methods.