Biology subjects

Turcotte, R.

Publications and source records attributed to Turcotte, R..

3 recordsLinked to original sources

bioRxiv2020

Compact and contactless reflectance confocal microscope for neurosurgery

Visual guidance at the cellular level during neurosurgical procedures is essential for complete tumour resection. We present a compact reflectance confocal microscope with a 20 mm working distance that provided <1.2 {micro}m spatial resolution over a 600 {micro}m x 600 {micro}m field of view in the near-infrared region. A physical footprint of 200 mm x 550 mm was achieved using only standard off-the-shelf components. Theoretical performance of the optical design was first evaluated via commercial Zemax software. Then three specimens from rodents: fixed brain, frozen calvaria and live hippocampal slices, were used to experimentally assess system capability and robustness. Results show great potential for the proposed system to be translated into use as a next generation label-free and contactless neurosurgical microscope.

neuroscience↗

bioRxiv2020

Two-photon fluorescence imaging of live neurons using a multimode optical fiber

Multimode optical fibers (MMFs), combined with wavefront control methods, have achieved minimally-invasive in vivo imaging of neurons in deep-brain regions with diffraction-limited spatial resolution. Here, we report a method for volumetric two-photon fluorescence imaging with a MMF-based system requiring a single transmission matrix measurement. Central to this method is the use of a laser source able to generate both continuous wave light and femtosecond pulses. The chromatic spreading of pulses generated an axially elongated excitation focus, which we used to demonstrate volumetric imaging of neurons and their dendrites in live rat brain slices through a 60 m-core MMF.

neuroscience↗

bioRxiv2018

Optical alignment device for two-photon microscopy

Two-photon excitation fluorescence microscopy has revolutionized our understanding of brain structure and function through the high resolution and large penetration depth it offers. Investigating neural structures in vivo requires gaining optical access to the brain, which is typically achieved by replacing a part of the skull with one or several layers of cover glass windows. To compensate for the spherical aberrations caused by the presence of these layers of glass, collar-correction objectives are typically used. However, the efficiency of this correction has been shown to depend significantly on the tilt angle between the glass window surface and the optical axis of the imaging system. Here we expand these observations and characterize the effect of the tilt angle on the collected fluorescence signal with thicker windows (double cover glass) and compare these results with an objective devoid of collar-correction. Finally, we present a simple optical alignment device designed to rapidly minimize the tilt angle in vivo and align the optical axis of the microscope perpendicularly to the glass window, thereby significantly improving the imaging quality. The performance of the device is demonstrated in an in vivo setting and a tilt-correction procedure is described, enabling the accurate alignment (<0.2{degrees}) of the cover glass with the imaging plane in only few iterations.

neuroscience↗