Relaxivity of Gadobutrol and Gadoteric Acid in Cerebrospinal Fluid at 3T

The aim was to estimate T1 relaxivity of gadobutrol and gadoteric acid in cerebrospinal fluid (CSF) at 3T, to support research on CSF-flow and the glymphatic system in humans utilizing T1 mapping after intrathecal injection.

Using a phantom, relaxivity was estimated for gadobutrol and gadoteric acid in lumbar CSF and an isotonic solution. All samples were scanned simultaneously using the variable flip angle method with B1 correction, repeated six times on one 3T scanner, and once on a second 3T scanner. Difference in relaxivity between CSF and the isotonic solution were evaluated from the repeated measurements.

There was a significant difference in relaxivity between CSF and the isotonic solution for both gadobutrol and gadoteric acid. The relaxivity for gadobutrol for the respective scanners was estimated to 3.02 ± 0.09 vs. 3.63 L mmol^-1 s^-1 in CSF and 2.35 ± 0.05 vs. 2.74 L mmol^-1 s^-1 in isotonic solution. For gadoteric acid, corresponding results were 2.47 ± 0.02 vs. 2.91 L mmol^-1 s^-1 in CSF and 2.37 ± 0.03 vs. 2.8 L mmol^-1 s^-1 in isotonic solution. Between the scanners, there was a high correlation (R² 0.998) but an 18% scaling difference in the T1 relaxation rates and corresponding relaxivities.

The relaxivity was higher in CSF than in the isotonic solution, particularly for gadobutrol. Systematic differences in relaxivity between scanners may potentially be corrected using a scaling factor derived from the T1 time of baseline CSF. For CSF studies using T1 mapping with a gadolinium-based contrast agent, we recommend using a CSF-specific relaxivity constant.