Intracellular activity-type and parameter estimation from dynamic optical coherence tomography signals

Dynamic optical coherence tomography (DOCT) is the combination of sequential OCT measurement and subsequent analysis of time sequence signals. However, detailed intracellular activity cannot be obtained from DOCT values. In this study, we proposed a method to estimate the intracellular activity type and its motion parameters from DOCT. We used three DOCT algorithms with two resolutions of OCT for estimation. The three DOCT metrics are computed from a single OCT time sequence. The low-resolution OCT image was generated from that of high-resolution by applying the Gaussian filter to the complex OCT data. First, we utilized differences in the resolution dependencies of DOCT to identify whether the type of motion was random ballistic or monodirectional-flow. We investigated the dependency of DOCT on resolution for each motion type by numerical simulation. The motion speed and dynamic scatterer ratio (DSR) are estimated by using DOCT fitting curve against speed and DSR. In mono-directional flow, the flow direction is also estimated from the fitted DOCT curves in the anisotropic resolutions. Numerical simulation was also used to generate the DOCT values. In addition, the measurement was performed to estimate the motion type and its parameters of biological sample. The tumor spheroid was measured by using 840-nm spectral domain OCT. The proposed method determined the motion in the spheroid sample as random ballistic motion, with more scatterers with smaller speed in the spheroid periphery and fewer scatterers with larger speed in the spheroid core.