T2-Weighted T1 Mapping and Automated Segmentation of CSF: Assessment of Solute Gradients in the Healthy Brain

Cerebrospinal fluid (CSF) serves as a medium for nutrient delivery and waste clearance. The T1 relaxation rate, R1, can be used to measure the concentration of intrinsic solutes and extrinsic contrast agents.

To implement a method for R1 mapping and segmentation of CSF and to use this method to explore how R1 of CSF relates to protein content and gadobutrol after intrathecal administration.

Prospective cohort study, complemented by phantom analysis.

Ten healthy control subjects (mean age 65.5 ± 4.4 years, range 57-72 years; five males and five females) and protein- and gadobutrol-gradient phantom.

3 T Philips Ingenia scanner; 3D T2W mixed inversion recovery spin-echo (T2W-mixed IRSE) sequence and 3D T1W turbo field echo (3D T1W-TFE).

R1 maps were calculated by combining IR and SE data. An automated segmentation method derived from FreeSurfer employed SE data for CSF segmentation and T1W-TFE for anatomical reference. CSF was collected by lumbar puncture for protein measurements, and 0.25 mmol gadobutrol was injected intrathecally. Post-contrast assessments were performed at 3, 24, 48, and 72 h.

One-way ANOVA, followed by a post hoc Tukey HSD test, and simple and multiple linear regression analysis; significance level of 0.05.

R1 of ventricular CSF 0.216 ± 0.001 s^-1 was significantly lower than that surrounding the cerebellum 0.225 ± 0.001 and cerebrum 0.228 ± 0.002 and correlated with lumbar protein concentration (R ² = 0.56). Peak gadobutrol concentrations were 101 ± 84 μM in ventricles, 185 ± 89 μM in cerebellar SAS and 166 ± 91 μM in cerebral SAS. Corresponding concentrations were 6 ± 4, 17 ± 8, and 37 ± 18 μM at 72 h.

Intrinsic R1 of CSF in the subarachnoid space correlated with protein content. Intracranial CSF enrichment after intrathecal administration of gadobutrol showed a large variation among healthy volunteers.

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