Transverse relaxation of cerebrospinal fluid depends on glucose concentration

To evaluate the biophysical processes that generate specific T₂ values and their relationship to specific cerebrospinal fluid (CSF) content.

CSF T_2s were measured ex vivo (14.1T) from isolated CSF collected from human, rat and non-human primate. CSF T_2s were also measured in vivo at different field strength in human (3 and 7T) and rodent (1, 4.7, 9,4 and 11.7T) using different pulse sequences. Then, relaxivities of CSF constituents were measured, in vitro, to determine the major molecule responsible for shortening CSF T₂ (2s) compared to saline T₂ (3s). The impact of this major molecule on CSF T₂ was then validated in rodent, in vivo, by the simultaneous measurement of the major molecule concentration and CSF T₂.

Ex vivo CSF T₂ was about 2.0s at 14.1T for all species. In vivo human CSF T₂ approached ex vivo values at 3T (2.0s) but was significantly shorter at 7T (0.9s). In vivo rodent CSF T₂ decreased with increasing magnetic field and T₂ values similar to the in vitro ones were reached at 1T (1.6s). Glucose had the largest contribution of shortening CSF T₂in vitro. This result was validated in rodent in vivo, showing that an acute change in CSF glucose by infusion of glucose into the blood, can be monitored via changes in CSF T₂ values.

This study opens the possibility of monitoring glucose regulation of CSF at the resolution of MRI by quantitating T₂.