Visible light optical coherence microscopy of the brain with isotropic femtoliter resolution in vivo.

Alfredo Dubra // Publications // Jan 15 2018

PubMed ID: 29328237

Author(s): Merkle CW, Chong SP, Kho AM, Zhu J, Dubra A, Srinivasan VJ. Visible light optical coherence microscopy of the brain with isotropic femtoliter resolution in vivo. Opt Lett. 2018 Jan 15;43(2):198-201. doi: 10.1364/OL.43.000198. PMID 29328237

Journal: Optics Letters, Volume 43, Issue 2, Jan 2018

Most flying-spot optical coherence tomography and optical coherence microscopy (OCM) systems use a symmetric confocal geometry, where the detection path retraces the illumination path starting from and ending with the spatial mode of a single-mode optical fiber. Here we describe a visible light OCM instrument that breaks this symmetry to improve transverse resolution without sacrificing collection efficiency in scattering tissue. This was achieved by overfilling a water immersion objective on the illumination path while maintaining a conventional Gaussian mode detection path (1/e2 intensity diameter ∼0.82 Airy disks), enabling ∼1.1  μm full width at half-maximum (FWHM) transverse resolution. At the same time, a ∼0.9  μm FWHM axial resolution in tissue, achieved by a broadband visible light source, enabled femtoliter volume resolution. We characterized this instrument according to paraxial coherent microscopy theory and, finally, used it to image the meningeal layers, intravascular red blood cell-free layer, and myelinated axons in the mouse neocortex in vivo through the thinned skull.