High-fidelity multimode fibre-based endoscopy for deep brain in vivo imaging

Abstract

Progress in neuroscience relies on new techniques for investigating the complex dynamics of neuronal networks. An ongoing challenge is to achieve minimally invasive and high-resolution observations of neuronal activity in vivo inside deep brain areas. Recently introduced methods for holographic control of light propagation in complex media enable the use of a hair-thin multimode optical fibre as an ultranarrow imaging tool. Compared to endoscopes based on graded-index lenses or fibre bundles, this new approach offers a footprint reduction exceeding an order of magnitude, combined with a significant enhancement in resolution. We designed a compact and high-speed system for fluorescent imaging at the tip of a fibre, achieving a resolution of 1.18 ± 0.04 µm across a 50-µm field of view, yielding 7-kilopixel images at a rate of 3.5 frames/s. Furthermore, we demonstrate in vivo observations of cell bodies and processes of inhibitory neurons within deep layers of the visual cortex and hippocampus of anaesthetised mice. This study paves the way for modern microscopy to be applied deep inside tissues of living animal models while exerting a minimal impact on their structural and functional properties.

Physical Layer Security in Multimode Fiber Optical Networks

“…Using the MMF as an flexible endoscope, the aim is to generate scanning focal spots at the end of the fiber. Therefore it is obvious to choose diffraction limited focal spots [23,26,25] as the T M basis. Another suitable basis to describe light transmission through an MMF is a basis of plane waves with varying spatial frequencies [24].…”

“…Nowadays, the MMF is a key device in several fields of research. They are used in biophotonical applications [19,20,21,22,23,24,25,26] to gain access to hard-to-reach areas due to their flexibility and high number of degrees of freedom in a minimum space. These properties are particularly helpful for image transmission using the MMF as an ultrathin endoscope.…”

Transmission of natural scene images through a multimode fibre

“…Full a priori knowledge of the input image and fibre * Daniele.Faccio@glasgow.ac.uk, Roderick.Murray-Smith@glasgow.ac.uk details could allow to numerically model the optical propagation [6], reconstruct the transmission matrix and then unscramble the output data, but in practice this can be extremely hard. Methods have been developed that allow to shape the input beam profile so as to focus the output field into a single spot that can then be scanned [7][8][9][10][11] with an emphasis on endoscopy [12][13][14][15]. Notwithstanding this notable progress, the development of a viable method that allows to unscramble the speckle patterns and thus retrieve high resolution, general image information in real time is an open challenge.…”

In vivo testing of a bioresorbable phosphate‐based optical fiber

“…The use of such probes for long‐term sensing is problematic as well because the risk of the breakage increases with time in the body and the ex‐plantation after their use can induce further damage. This issue is critical especially in case of single‐fiber imaging of brain tissue , which is very sensitive.…”