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A lensless endoscope based on optical techniques

28/07/2015

By Optitec

Usage of optical techniques to create a lensless endoscope. An evolution in optics which will impact life science

A persistent challenge in two-photon excited fluorescence (2PEF) imaging is deep imaging in tissue. In particular, a challenge lies in recording neuronal activity with single-cell resolution deep in the living brain. 2PEF microscopy is a method of choice for imaging the activity of neurons but due to tissue scattering, its imaging depth is limited to 100 microns – 1 mm. Responding to this challenge, this project proposes to develop methodology allowing to acquire a 2PEF image at the tip of a wave guide – a multi-core fiber – with the same speed and flexibility as a 2PEF  microscope. This wave guide will constitute the flexible probe of a “lensless endoscope”. The objective is to develop a 2PEF lensless endoscope having a flexible probe with diameter 200 microns, small enough to permit deep insertion into the living mouse brain for deep tissue image acquisition.

To fulfill the objective, an interdisciplinary approach will be taken. The instrumental and methodological development will be guided by a targeted neuroimaging experiment, simultaneous imaging of neuronal activity in the hippocampus and entorhinal cortex of a living mouse. Multi-core fibers will be designed and fabricated explicitly for the project. To realize the lensless endoscope, imaging through multicore fibers will be achieved through an integrality of interferometry, holography, wave front shaping, and adaptive optics. The project has several novel aspects. The multi-core fibers developed will be the first ones optimized for 2PEF imaging. The endoscope developed represents the uncharted territory of nonlinear imaging through a waveguide. Its use in conjunction with existing neuroimaging methods represents a novel way of probing long-range functional connections in the brain. The results obtained will enable other nonlinear image contrasts and methods in endoscopes, opening even more new horizons in brain imaging.

The coordinator of this project is M. Esben Ravn ANDRESEN, researcher from Institution Institut Fresnel – esben.andresen@fresnel.fr

The project is totally unique at the national level in France.