Listening to the Brain With Photoacoustics

Photoacoustic imaging (PAI), providing the unique contrast of optical absorption and the superb scalability of spatial resolution and penetration, has emerged as an enabling technique in both basic and translational brain research. In this paper, first, mechanisms behind neuro-PAI of endogenous absorber-encoded functional information (e.g., the concentration of hemoglobin, the oxygen saturation of hemoglobin, blood flow, oxygen metabolism, and water accumulation) and exogenous probe-labeled molecular targets (e.g., neural activity, glucose uptake, aberrant protein aggregation, and malignancy) are introduced. Then, two technical innovations-functional connectivity photoacoustic tomography and high-speed functional photoacoustic microscopy-for spatio-temporal interrogation of the brain at resting and activated states are highlighted, and two application niches in vascular cognitive impairment and brain cancer are discussed. Finally, the prospect of neuro-PAI is envisioned.