High-speed imaging with light-sheet fluorescence microscopy poses several challenges throughout the whole pipeline, from data acquisition in the lab to image stitching and post-processing. Here we present our custom hardware and software solutions that allow us to map large biological samples at the cellular level, e.g. large portions of human brain cortex. Our custom optical setup—a dual-view, inverted, light-sheet microscope—is capable of simultaneous two-color acquisition at a data rate of 1 GB/s. Our open source tools include the instrument’s data acquisition and control software and also cover volumetric image stitching and post-processing.
To understand the brain computation paradigms and the causal interactions in complex neuronal networks, we need methods and technologies to record and perturb neuronal distributions over large fields of view. In this application, two-photon (2P) imaging has become a cornerstone microscopy technique, widely used for deep optical access in biological samples and selective light targeting with submicrometric resolution. In parallel to structural and functional imaging, 2P optogenetics has represented a game-changer, allowing targeted stimulation of specific neural circuits. However, the long commutation times and refresh rates of traditional scanning methods substantially hinder near-simultaneous multi-site 3D stimulation. Acousto-optic deflectors (AODs), owing to their fastest scanning and refresh rates, can fulfil the temporal requirements for concurrent activation of sparsely distributed neurons. Nevertheless, their applicability to 2P optogenetics in large volumes has been limited so far by the massive efficiency drop along the optical axis during their use in axial scanning. To counteract this drawback, a compensation software module is frequently employed to flatten the power distribution throughout the volume. However, the power threshold is reduced to the minimum intensity value addressable, lowering the peak intensity released in the centre of the axial scan.
Here, we propose a unique approach for overcoming this drawback which provided lifted axial power distribution while maintaining a uniform lateral illumination range. We tested this method by the 2P photoactivation of optogenetic actuators in 3D in zebrafish larvae, showing how the probability of evoking an electrophysiological response and the relative neuronal activity amplitude improved by carefully optimizing the light targeting time on different axial planes.
In conclusion, fast and uniform axial light addressing with AODs enables unprecedented 3D 2P optostimulation, formerly not feasible. Furthermore, this approach can be adopted as an upgrade for existing microscopes designed for volumetric imaging, providing 3D multi-site imaging and random-access illumination.
In the past few years, Light Sheet Fluorescence Microscopy (LSFM) has become a cornerstone imaging technique for neuroscience, improving the quality and capabilities of 3D imaging. Selec-tive illumination of a single plane provides intrinsic optical sectioning and fast image recording, while minimizing out-of-focus fluorescence background, sample photo-damage and photobleach-ing. However, images acquired with LSFM are often affected by light absorption or scattering effects, leading to un-even illumination and striping artifacts. Here we present an optical solution for such problem, via fast multi-directional illumination of the sample, based on an Acousto-Optical Deflector (AOD). Using this device, we were able to pivot the beam respect the propagation axis, with a scanning rate faster than the detector acquisition rate, in order to average the shadows attenuation at different angles over time. We also demonstrate that this scanning AOD system is compatible with Digital Scanned laser Light-sheet fluorescence microscopy (DSLM). Furthermore, we provided a theoretical model of the beam pivoting, looking for the optimal beam parameters to optimize the detection efficiency. It has been done because we wanted to adapt such scanning technique to Confocal Light Sheet Microscopy (CLSM), which intrinsically shows an incompatibility between the beam pivoting and the finite size of a digital slit used to spatially filter out spurious signals. We partially solved the problem expanding the beam and using two cylindrical lenses to create an elliptical-Gaussian beam which enables to cover more the digital slit while pivoting the beam. We test its performance by acquiring several mouse brain areas, observing real-time shadows suppression while preserving confocal detection of the signal emitted by specific fluorophores. A comparison between such scanning beam illumination and a traditional static one has been carried out in term of contrast analysis, striping suppression and Point Spread Function response.
We still lack a detailed map of the anatomical disposition of neurons in the human brain. A complete map would be an important step for deeply understanding the brain function, providing anatomical information useful to decipher the neuronal pattern in healthy and diseased conditions. Here, we present several important advances towards this goal, obtained by combining a new clearing method, advanced Light Sheet Microscopy and automated machine-learning based image analysis. We perform volumetric imaging of large sequentially stained human brain slices, labelled for two different neuronal markers NeuN and GAD67, discriminating the inhibitory population and reconstructing the brain connectivity.
We still lack a detailed map of the anatomical disposition of neurons in the human brain. A complete map would be an important step for deeply understanding the brain function, providing anatomical information useful to decipher the neuronal pattern in healthy and diseased conditions. Here, we present several important advances towards this goal, obtained by combining a new clearing method, advanced Light Sheet Microscopy and automated machine-learning based image analysis. We perform volumetric imaging of large sequentially stained human brain slices, labelled for two different neuronal markers NeuN and GAD67, discriminating the inhibitory population and reconstructing the brain connectivity.
Confocal detection in digital scanned laser light-sheet fluorescence microscopy (DSLM) has been established as a gold standard method to improve image quality. The selective line detection of a complementary metal–oxide–semiconductor camera (CMOS) working in rolling shutter mode allows the rejection of out-of-focus and scattered light, thus reducing background signal during image formation. Most modern CMOS have two rolling shutters, but usually only a single illuminating beam is used, halving the maximum obtainable frame rate. We report on the capability to recover the full image acquisition rate via dual confocal DSLM by using an acousto-optic deflector. Such a simple solution enables us to independently generate, control and synchronize two beams with the two rolling slits on the camera. We show that the doubling of the imaging speed does not affect the confocal detection high contrast.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.