Spatial and temporal aberrator stability for real-time adaptive imaging.

Reported real-time adaptive imaging systems use near-field phase correction techniques, which are desired because of their simple implementation and their compatibility with current system architectures. Aberrator stability is important to adaptive imaging because it defines the spatial and temporal limits for which the near-field phase estimates are valid. Spatial aberrator stability determines the required spatial sampling of the aberrator, and temporal aberrator stability determines the length of time for which the aberration profile can be used. In this study, the spatial and temporal stability of clinically measured aberrations is reported for breast, liver, and thyroid tissue. Cross correlations between aberration estimates revealed aberrators to have azimuthal isoplanatic patch sizes of 0.44, 0.28, and 0.20 mm for breast, liver, and thyroid tissue, respectively, at 80% correlation. Axial isoplanatic patch sizes were 1.26, 0.76, and 1.80 mm for the same tissue, respectively, at 80% correlation. Temporal stability at 80% correlation was determined to be greater than 1.5 seconds for breast and thyroid tissue, and 0.65 seconds for the liver. The effects of noise, motion, and target nonuniformity on aberrator stability are characterized by simulations and experiments in tissue mimicking phantoms.