Side-view holographic endomicroscopy via a custom-terminated multimode fibre

Abstract

Microendoscopes based on optical fibres have recently come to the fore as promising candidates allowing in-vivo observations of otherwise inaccessible biological structures in animal models. Despite being still in its infancy, imaging can now be performed at the tip of a single multimode fibre, by relying on powerful holographic methods for light control. Fibre based endoscopy is commonly performed en face, resulting in possible damage of the specimen owing to the direct contact between the distal end of the probe and target. On this ground, we designed an all-fibre probe with an engineered termination that reduces compression and damage to the tissue under investigation upon probe insertion. The geometry of the termination brings the field of view to a plane parallel to the fibre’s longitudinal direction, conveying the probe with off-axis imaging capabilities. We show that its focusing ability also benefits from a higher numerical aperture, resulting in imaging with increased spatial resolution. The effect of probe insertion was investigated inside a tissue phantom comprising fluorescent particles suspended in agarose gel, and a comparison was established between the novel side-view probe and the standard en face fibre probe. This new concept paves the way to significantly less invasive deep-tissue imaging.

110 μm thin endo-microscope for deep-brain in vivo observations of neuronal connectivity, activity and blood flow dynamics

“…Importantly, we deployed side-view fibre probes 31 in our in vivo experiments, facilitating observation of tissue volumes off the fibre’s axis and thereby much less affected by the endoscope insertion (see Fig. 1 c and “Methods” for more details).…”

“…The whole geometry is similar to the experimental system described in ref. 31 . A collimated laser beam with a wavelength of 488 nm (Coherent Sapphire) is divided into a signal and a reference beams.…”

Holographic Manipulation of Nanostructured Fiber Optics Enables Spatially‐Resolved, Reconfigurable Optical Control of Plasmonic Local Field Enhancement and SERS

“…All-optical manipulation of nanoscale light-matter interaction on the output facet of an optical fiber, in turn, lays the ground for fully integrated plasmonic endoscopes based on both EOT and SERS phenomenology, potentially hosting a diverse ensemble of activatable plasmonic structures. Holographic imaging methods have been applied for fluorescence imaging through MMFs in tissue [42] and in living animals, [39,40] controlling the coupling between guided modes in MMFs and plasmonic structures could potentially add molecular sensing capability, with techniques such as deep learning, [22] guide star, [24] side view fibers [43] all able to improve the translatability of the approach.…”

Custom: terminated multimode fibre probe for holographic micro-endoscopy

“…Fibre-based endoscopy is commonly performed en face (Figure 1), resulting in possible damage of the specimen owing to the direct contact between the distal end of the probe and target region. A recent paper shows and describes the design of an all-fibre probe with an engineered termination that reduces compression and damage to the tissue under investigation upon probe insertion [2]. The termination geometry brings the field of view to a plane parallel to the fibre´s longitudinal direction, conveying the probe with off-axis imaging capabilities.…”

“…Illustrative scheme of en face performed fibre-based micro-endoscopy However, silica fibre probes with a diameter of about 100 microns are more susceptible to damage. In this work we present novel advanced approach for manufacturing side-view custom-terminated multimode fibre probes [2] with a reduced diameter, more durable protective layer, better imaging performance and compact shape.…”