Noninvasive magnetic resonance imaging technique for mapping cerebrospinal fluid and meningeal lymphatic flow

Abstract

Imaging in-vivo movement of cerebrospinal fluid (CSF) can be applied not only to diagnose the CSF disorders like hydrocephalus, but also to visualize and evaluate the CSF circulation for the waste clearance. In this study, we used single phase and multiphase alternate ascending/descending directional navigation (ALADDIN) MR imaging techniques, to image the CSF dynamics. We demonstrated in-plane sagittal CSF flow from single phase axial ALADDIN images, and also showed temporal change of CSF flow in aqueduct by using multiphase ALADDIN images. Single phase ALADDIN showed both feet to head (F→H) and head to feet (H→F) directional net flow of CSF, and the tendency of flow distribution was similar with conventional cine gated phase contrast imaging result. The multiphase ALADDIN data showed both dynamically tracked signal intensity and the direction of labeled CSF in aqueduct. Furthermore, the H→F direction data from multiphase ALADDIN was applied on spin labeling based kinetic model fitting. We estimated the CSF flow rate of H→F direction in aqueduct as 1.3017$\mu$l/sec. Through this study, we could get not only the dynamics of CSF from image, but also we could get the information of origination of imaging signals from CSF. In addition, recent studies showed meningeal lymphatic vessels significantly contribute to the clearance mechanisms of CSF and the immune system in central nervous system. Until recently, the techniques to image mLVs through MRI were using intravenous contrast agent or using time of flight technique for non-contrast agent technique. To image human dorsal meningeal lymphatic vessels (mLVs) in high resolution without contrast agent, we used inversion recovery ALADDIN (IR-ALADDIN) through coronal section of brain. We applied inversion RF pulses with 2300ms inversion time to suppress CSF signal around the mLVs. The IR-ALADDIN imaging technique clearly showed structural mLVs around the superior sagittal sinus (SSS). Also it showed the direction of dorsal mLVs mainly flowed through posterior to anterior axis which is opposite direction of SSS flow. To validate the result, the percent signal change value from mLVs, CSF, gray matter and SSS were confirmed to differ from each other’s. We expect that ALADDIN can be applied to study CSF circulation/clearance disorders and also study lymphatic vessels in human neurological diseases in the future.