In vivo high-resolution cortical imaging with extended-focus optical coherence microscopy in the visible-NIR wavelength range.

Visible light optical coherence tomography has shown great interest in recent years for spectroscopic and high-resolution retinal and cerebral imaging. Here, we present an extended-focus optical coherence microscopy system operating from the visible to the near-infrared wavelength range for high axial and lateral resolution imaging of cortical structures in vivo. The system exploits an ultrabroad illumination spectrum centered in the visible wavelength range (λc  =  650  nm, Δλ  ∼  250  nm) offering a submicron axial resolution (∼0.85  μm in water) and an extended-focus configuration providing a high lateral resolution of ∼1.4  μm maintained over ∼150  μm in depth in water. The system's axial and lateral resolution are first characterized using phantoms, and its imaging performance is then demonstrated by imaging the vasculature, myelinated axons, and neuronal cells in the first layers of the somatosensory cortex of mice in vivo.