Noninvasive whole-brain imaging of glymphatic dynamics

Cerebrospinal fluid circulation through the glymphatic system plays a crucial role in removing metabolic waste from the central nervous system. However, the mechanism underlying the brain-wide glymphatic dynamics is not yet fully understood, in part due to the lack of glymphatic imaging technologies on deep brains. Here, we report a hybrid imaging technology that integrates three-dimensional photoacoustic tomography and ultrasound localization microscopy (3D-PAULM), enhanced by a photoacoustic dye with strong optical absorption in the second nearinfrared window (NIR-II). 3D-PAULM allows for continuous, noninvasive, whole-brain imaging in mice through intact skull, providing superresolution mapping of the brain vasculature and highly sensitive tracing of the NIR-II dye in the glymphatic system. Using 3D-PAULM, we investigated the glymphatic function impaired by ischemic stroke, aging, and anesthesia. Our results provide insights into glymphatic transport under various physiological as well as pathological conditions and establish 3D-PAULM as a valuable tool for preclinical glymphatic research.