Size estimation of mixed free-floating sub-resolution spherical scatterers utilizing adaptive scanning optical coherence tomography.

Optical coherence tomography (OCT) is a volumetric imaging technique that enables real-time assessment of biological tissues with micrometer-scale resolution. This enables OCT to also offer the potential to estimate scatterer size. However, in cases where the axial and lateral resolution of the OCT system are larger than the target scatterer, it is difficult to assess the scatterer size directly within the OCT space domain. This paper presents a workflow to estimate diameters of individual free-floating spherical particles within OCT volumes, leveraging adaptive scanning, spectroscopic OCT, and Mie theory. Using this workflow, we demonstrate the capability to estimate individual microbead diameters ranging from 6 to 10 μm, both in isolation and within mixed solutions with 12 × speed up than the previous method. The results indicate that the proposed Mie backscattering approach yields size estimations that were statistically equivalent to labeled values. In experiments with a mixed solution containing microbeads of 6 μm, 8 μm, and 10 μm diameters, our method successfully differentiated the three bead sizes through histogram analysis.