New imaging combines light and sound to watch brain oxygen supply in real time
The brain is a black box of densely packed neurons, blood vessels and immune cells, all locked away in a sealed skull. WashU's Song Hu has dedicated his career to unlocking that puzzle box by developing new ways to "see" inside. His team's newest innovation could give researchers a new view of how brain cells and blood vessels work together and what happens when the coupling between the two…
Scientists at Washington University in St. Louis have developed a novel imaging technique that simultaneously combines light and sound to observe brain oxygen supply in real time. This new approach, created by Professor Song Hu and his team in the McKelvey School of Engineering, integrates two-photon microscopy and photoacoustic microscopy (TPM-PAM) to provide unprecedented insights into the brain's vasculature and its interaction with neurons.
Traditionally, researchers use two-photon microscopy to image neuronal activity by flooding the brain with fluorescent probes, while photoacoustic microscopy uses light-generated sound waves to record blood flow and oxygenation. However, the new TPM-PAM system allows researchers to see both aspects of brain function at the cellular level, revealing how oxygen delivery from blood vessels affects neuronal activity and vice versa.
This real-time visualization could significantly advance our understanding of neurodegenerative diseases, stroke, and other conditions related to neurovascular coupling—the process by which blood vessels deliver oxygen and nutrients to neurons. By integrating these two techniques, the new system enables precise, cell-scale interventions alongside simultaneous measurements of neuronal activity and oxygen delivery.
This breakthrough, reported in Nature Communications, overcomes the technical challenge of merging light and sound waves by using an optically transparent acoustic sensor. This sensor, made from a polymer micro-ring resonator on a piece of glass, preserves the optical imaging performance of TPM while allowing the acoustic signal to be converted into a measurable change in light.
The ability to image both neuronal calcium activity and red-blood-cell oxygen delivery simultaneously opens up new possibilities for understanding the complex relationship between brain function and its vasculature. This technology could also improve clinical imaging by providing a more accurate cellular-scale picture of neurovascular coupling, potentially leading to better interpretations of indirect signals used in functional MRI.
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