Peking University - Juntendo University Joint Symposium on Brain and Skin Diseases: Measurement of the Brain Extracellular Space Using Tracer-Based MRI

Neurons have been considered the most important functional unit of the brain and have attracted the most attention in neurobiology. Neural cells occupy 70%-80% of the whole brain volume, but until now, our current knowledge of neural circuit cannot explain all the neurological conditions of the brain. Thus, it is also important to consider the influence of the extracellular space (ECS) around neural cells, which contains the brain interstitial fluid (ISF). This paper includes the anatomy of the brain ECS under physiological condition, the in vivo measurement techniques of brain ECS, and the divisions of brain ECS. Moreover, the implications of ECS knowledge of basic neuroscience and clinical applications are introduced, including the brain tissue engineering and the local drug delivery via ECS.