Photoacoustic imaging for neurobiology

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Principal investigator: Thomas Chaigne

There is currently no technique to image neuronal activity with cellular resolution (∼ 10 µm), with large fields of view (∼ 1 cm ) deep inside the brain (> 1 mm), while resolving single action potentials (∼ 1 ms).
Most efforts are devoted to scaling up multi-photon fluorescence microscopy to image increasingly larger and deeper populations of neurons, but these techniques are inherently limited by light scattering to shallow depths.
So we add another kind of waves to help us out: ultrasounds. When absorbers (like hemoglobin, or calcium indicators) heat up under pulsed illumination, they emit pressure waves that are not scattered by soft tissue, and can therefore be externally measured to reconstruct the inner optical absorption: this is the principle of photoacoustic imaging.
We believe that this new technique can have a significant impact in neurobiology, by providing non-invasive access to the deeper layers of the cortex and to the hippocampus.

Fast interrogation wavelength tuning for all-optical photoacoustic imaging
Jérémy Saucourt, Antonin Moreau, Julien Lumeau, Hervé Rigneault, and Thomas Chaigne
Optics Express 31, 11164-11172 (2023)