Real-time monitoring of cerebrospinal fluid flow and assessment of brain waste clearance via photoacoustic imaging

The assessment of cerebrospinal fluid (CSF) is crucial for understanding the maintenance of brain health, as it plays a vital role in removing metabolic waste and neurotoxic proteins. While existing imaging methods such as MRI and PET provide CSF information, they have limitations in temporal resolution, anatomical contrast, or invasiveness aspects. Here, we demonstrate the application of whole-body photoacoustic computed tomography (PACT) for noninvasive, high-resolution imaging of CSF flow and glymphatic function in small animals. Using indocyanine green (ICG) as a CSF tracer, we successfully visualized three-dimensional CSF pathways following intrathecal (IT) injection in mice. Our system enabled real-time monitoring of CSF influx into the cisterna magna under different anesthesia types, revealing enhanced glymphatic flow in ketamine/xylazine-anesthetized mice compared to those under isoflurane. Furthermore, we compared long-term tracer clearance between wild-type (WT) and Alzheimer’s disease (AD) mouse models, observing significantly impaired waste removal from the brain striatum in AD mice. This study highlights the potential of PACT to serve as a valuable tool in preclinical neuroimaging and glymphatic analysis, combining molecular sensitivity with anatomical detail, and offering a safer alternative to conventional methods.