Biological processes at the interface of cell and developmental biology are highly dynamic and take place on several spatial and temporal scales. Methods allowing to visualise and quantify these processes across scales are becoming indispensable for modern biological and biomedical research and applications. Fluorescent microscopy has emerged as a powerful technique to acquire spatial and temporal information in living samples and while considerable progress has been achieved over the past 20 years, fast volumetric imaging is still in its infancy. Particularly, imaging the developing heart as it beats or visualising neuronal activities in the brain requires volumetric acquisition speeds which are beyond current technology.

Our project aims to develop the conceptual, technological and computational framework to push fluorescent volumetric imaging with single photon sensitivity beyond current limitations, to eventually become a standard tool for modern biomedical applications. To achieve this, a paradigm change on how data is acquired and processed is required, moving from the standard fluorescent microscopy acquisition order that separates spatial and temporal aspects, towards an interleaved spatio-temporal acquisition scheme. This novel acquisition scheme requires sensors with single photon detection sensitivity and temporal resolution in the sub-nanosecond range (expertise of E.C). Furthermore, highly efficient optical illumination and detection schemes are needed to ensure high quality data acquisition amenable to large scale data processing and reduction of phototoxic effects for the biological samples (expertise of L.H.). Finally, strong industrial expertise and market access (Luxendo GmbH) is indispensable to turn the new concept into microscopes usable by the broader biological community. The partners of the project will work closely together to achieve the goal.

Our project will be based on a combination of the light sheet illumination scheme with state-of-the-art single-photon avalanche diode (SPAD) arrays (SwissSPAD2). The inherent optical sectioning capabilities of light sheet microscopy together with its optimal use of illumination light makes it an ideal concept for fast volumetric imaging. Temporal synchronisation of rapidly oscillating light sheets together with time-stamped photon events recorded by the SPAD array will enable unprecedented volumetric imaging speeds. Our approach will outperform other volumetric imaging techniques in acquisition speed, spatial resolution and image quality.