title: Phase-gradient contrast in thick tissue with a scanning microscope.
abstract: It is well known that the principle of reciprocity is valid for light traveling even through scattering or absorptive media. This principle has been used to establish an equivalence between conventional widefield microscopes and scanning microscopes. We make use of this principle to introduce a scanning version of oblique back-illumination microscopy, or sOBM. This technique provides sub-surface phase-gradient and amplitude images from unlabeled tissue, in an epi-detection geometry. That is, it may be applied to arbitrarily thick tissue. sOBM may be implemented as a simple, cost-effective add-on with any scanning microscope, requiring only the availability of an extra input channel in the microscope electronics. We demonstrate here its implementation in combination with two-photon excited fluorescence (TPEF) microscopy and with coherent anti-Stokes Raman scattering (CARS) microscopy, applied to brain or spinal cord tissue imaging. In both cases, sOBM provides information on tissue morphology complementary to TPEF or CARS contrast. This information is obtained simultaneously and is automatically co-registered. Finally, we show that sOBM can be operated at video rate.
authors.affiliation: Boston University, Department of Biomedical Engineering, 44 Cummington St., Boston, MA 02215 USA.
authors.forename: J
authors.initials: J
authors.lastname: Mertz
authors.affiliation: Centre de Recherche Université Laval Robert-Giffard (CRULRG), Université Laval, Québec, Qc, G1J 2G3, Canada ; Centre dOptique, Photonique et Laser (COPL), Université Laval, Québec, Qc, G1V 0A6, Canada.
authors.forename: A
authors.initials: A
authors.lastname: Gasecka
authors.affiliation: Centre de Recherche Université Laval Robert-Giffard (CRULRG), Université Laval, Québec, Qc, G1J 2G3, Canada ; Centre dOptique, Photonique et Laser (COPL), Université Laval, Québec, Qc, G1V 0A6, Canada.
authors.forename: A
authors.initials: A
authors.lastname: Daradich
authors.affiliation: Boston University, Biology Department, 24 Cummington St., Boston, MA 02215 USA.
authors.forename: I
authors.initials: I
authors.lastname: Davison
authors.affiliation: Centre de Recherche Université Laval Robert-Giffard (CRULRG), Université Laval, Québec, Qc, G1J 2G3, Canada ; Centre dOptique, Photonique et Laser (COPL), Université Laval, Québec, Qc, G1V 0A6, Canada.
authors.forename: D
authors.initials: D
authors.lastname: Coté
keywords: (110.0180) Microscopy; (180.5810) Scanning microscopy; (290.7050) Turbid media