Glymphatic imaging using MRI

• Published in: Journal of magnetic resonance imaging Vol. 51; no. 1; pp. 11 - 24
• Main Authors: Taoka, Toshiaki, Naganawa, Shinji
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01.01.2020; Wiley Subscription Services, Inc
• Subjects: Animals; Brain; Cerebrospinal fluid; Contrast agents; Contrast Media; Diffusion; diffusion imaging; Fluorescence; Fluorescent indicators; Gadolinium; glymphatic system; Glymphatic System - diagnostic imaging; Glymphatic System - physiology; Humans; Image Enhancement - methods; In vivo methods and tests; interstitial fluid; Intravenous administration; Isotopes; Magnetic resonance imaging; Magnetic Resonance Imaging - methods; Mass transport; Medical imaging; Mice; Neuroimaging; Phase contrast; Stable isotopes; Studies; Tracers; Transportation systems; interstitial fluid; magnetic resonance imaging; diffusion imaging; glymphatic system; cerebrospinal fluid; contrast media
• ISSN: 1053-1807; 1522-2586; 1522-2586
• DOI: 10.1002/jmri.26892

In recent years, the existence of a mass transport system in the brain via cerebrospinal fluid (CSF) or interstitial fluid (ISF) has been suggested by many studies. The glymphatic system is hypothesized to be a waste clearance system of the CSF through the perivascular and interstitial spaces in the brain. Tracer studies have primarily been used to visualize or evaluate the waste clearance system in the brain, and evidence for this system has accumulated. The initial study that identified the glymphatic system was an in vivo tracer study in mice. In that study, fluorescent tracers were injected into the cisterna magna and visualized by two‐photon microscopy. MRI has also been used to evaluate glymphatic function primarily with gadolinium‐based contrast agents (GBCAs) as tracers. A number of GBCA studies evaluating glymphatic function have been conducted using either intrathecal or intravenous injections. Stable isotopes, such as 17O‐labeled water, may also be used as tracers since they can be detected by MRI. In addition to tracer studies, several other approaches have been used to evaluate ISF dynamics within the brain, including diffusion imaging. Phase contrast evaluation is a powerful method for visualizing flow within the CSF space. In order to evaluate the movement of water within tissue, diffusion‐weighted MRI represents another promising technique, and several studies have utilized diffusion techniques for the evaluation of the glymphatic system. This review will discuss the findings of these diffusion studies. Level of Evidence: 5 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2019. J. Magn. Reson. Imaging 2020;51:11–24.