Nano-sensitive optical coherence tomography (nsOCT) for depth resolved characterization of 3D submicron structure

Nowadays optical coherence tomography (OCT) is a rapidly developing technique with various applications, including biomedical imaging and diagnosis. One of the main shortcomings of current OCT techniques is low resolution and sensitivity to structural changes (typically about 10 microns). The best ultra-high resolution OCT techniques demonstrate sensitivity to structural changes and depth resolution of about 1 micron. Since many applications of interest (such as cancer) depend on structural changes at the nanoscale, OCT would definitely benefit from improved structural resolution and sensitivity. A new spectral encoding of spatial frequency (SESF) approach for quantitative characterization of the structure with nanoscale sensitivity has been developed recently. Ability to map axial structural information into each pixel of a 2D image with nanoscale sensitivity has been demonstrated and application of this approach to 3D microscopic imaging has been discussed. Here we present a novel technique, nano-sensitive OCT (nsOCT), to dramatically increase sensitivity of the OCT to structural changes. We propose to directly translate information about particular structure from Fourier domain to the image domain and map this information into the corresponding location within the 3D OCT image. As a result, submicron axial structure can be visualized and nanoscale structural alterations for each volume of interest within the 3D OCT image can be detected. Preliminary results show that using nsSOCT, based on conventional spectral domain OCT system with resolution 30 x 30 x 12 μm, it is possible to detect structural changes within scattering sample as small as 30 nm.