The aim of this study was to evaluate the feasibility of kinetic analysis of cerebrospinal fluid (CSF) using 17O-labeled water tracer. Four subjects (two idiopathic normal pressure hydrocephalus (iNPH) and two possible AD dementia patients) were prospectively included. Injectable formulation of 17O-labeled water containing 10 mol% of H217O (PSO17), was intrathecally administered to the subjects with the lateral decubitus position between the 3rd and 4th lumbar vertebrae. MRI acquisitions were performed in four-time points, before PSO17 administration, 1, 8, and 24 h after PSO17 administration. The 3-dimensional fast spin echo sequence was used. After image registration for all four-time points data, polygonal regions of interest (ROIs) were set in the 14 regions to obtain the signal intensity of CSF. Each signal intensity within the ROI was converted to 17O concentration [%]. The peak concentration at one hour after administration, the slope of concentration changes after PSO17 administration [%/s], and the root mean square error (RMSE) for evaluating the performance of a fitting were calculated. There was no significant difference in peak concentration between the iNPH and AD group. The slope in the AD group (-2.25 ± 1.62 × 10-3 [%/h]) was significantly smaller than in the iNPH group (-1.21 ± 2.31 × 10-3 [%/h]), which suggests the speed of CSF clearance in the iNPH group was slower than AD group. The RMSE indicating the fit to the concentration change in the AD group (4.86 ± 4.74 × 10-3) was also significantly smaller than in the iNPH group (8.64 ± 7.56 × 10-3). The kinetic evaluation of CSF using 17O-labeled water was feasible, and this preliminary study suggests that the differentiation of iNPH and possible AD dementia can be achieved using this method.
Keywords: (17)O; Cerebrospinal fluid; Water kinetics.
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