Imaging of cortical structures and microvasculature using extended-focus optical coherence tomography at 1.3 μm

Extended-focus optical coherence tomography (xf-OCT) is a variant of optical coherence tomography (OCT) wherein the illumination and/or detection modes are engineered to provide a constant diffractionless lateral resolution over an extended depth of field (typically 3 to 10x the Rayleigh range). xf- OCT systems operating at 800 nm have been devised and used in the past to image brain structures at high-resolution in vivo, but are limited to similar to 500 mu m in penetration depth due to their short illumination wavelength. Here we present an xf- OCT system optimized to an image deeper within the cortex by using a longer illumination central wavelength of 1310 nm. The system offers a lateral resolution of 3 and 6.5 mu m, over a depth of 900 mu m and >1.5 mm using a 10x and 5x objective, respectively, in air. We characterize the system's resolution using microbeads embedded in PDMS and demonstrate its capabilities by imaging the cortical structure and microvasculature in anesthetized mice to a depth of similar to 0.8 mm. Finally, we illustrate the difference in penetration depths obtainable with the new system and an xf- OCT system operating at 800 nm. (C) 2018 Optical Society of America.